Winter layers

Nice looking boots (Shimano M087s)
Light rain I sometimes get caught in Shimano road clip boots. Tuck wet pants into socks yet seem to only get a wet sole spot on each foot.
Wet weather bike has flat pedals (and rear guard).
These are the shoes/boots I use.
Dunlop Volleys. Tend to get wet quick, pants tucked into socks. But stay grippy and change of socks is quick enough.
I like boots with long laces but note that I ride fixie with Velcro road shoes (just in case, never wet weather, it's a track bike with brakes).
Long laces lock ever extra turn under the lip of boot entry hence stay all day, all night during summer/winter use. During storm I find length useful to lash wet pants over boot neck.
I don't understand modern overlays. A couple of rubber bands would do the same thing if riding with long neck boots. Just typing because it works well here.
Short laces and rubber bands probably much safer especially since if lace lets go it's enveloped inside wet pants yet fair go too, most people have tied laces daily since they were child hence they're probably well practiced.
Top layer I use a beanie under a warm high shelf hoodie under a spray jacket. Can cover all except eyeglasses hole off face and that's hot at zero degrees with shorts under spray pants because legs get hot too. If going colder a simple thermo layer is light and thin and would be comfortable down to minus 10 while riding. Two thermos, less efforted ride and comfortable. Only wind that gets past is eye level and it's not cold because throat is raw and head maybe hotter. Often removing bits to cool down such as beanie or under spray light rain jackets zipper.
I guess a lot of you don't have baggy calf pants problem but I just wear clothes I'd sail in. (Boots different again, wet ones)

I commute in & around Belfast  all year round when possible. Our winters are pretty horrible most of the time, grim, cold, bloody wet & windy  & I cycle most weekends too so our stuff needs to be  up too the job. A lot of stuff is just not designed for a damp icy cold windy / rain but I am another +1 for pretty much any of Galibier.cc products & I find them very reasonably priced - everyone has a budget of course.

Their deep winter gloves are 2nd to none (honestly) & I've have Castelli, Campy's, Seal skins & Gore.  Galibier win everytime for warmth & wind protection even when wet but they are on the bulky side so may not be the most ideal for traffic nipping  etc. That said mine only ever come out in single digit temps, they are warm!

The Arctic overshoes are serious heavy duty  so need to have a worthwhile commute to warrant the effort to put on - tip size up if buying they arre tight. Also have a DHB heavy duty pair which are used alot. 

Galibier do some very cool funky design base layers too which are warm! but think wiggle's dhb merinos are great too.

Don't owe but heard many good reports on the Mistral.

I have a shakedry, best waterproof I have ever experienced bare none but I only use it for weekend miles, too good for commuting, need something a bit more hard wearing as I carry a rucksack & commute on a fixie so you sweat no matter what the temp! 

I ride in similar conditions to you, although dodge the rain when possible.  Craft make some great baselayers; I wear one of those with a Gore thermo jersey of some kind and a North Wave fluoro jacket, this all keeps my top half warm down to about 3 degrees.  The Gore jersey twp extra little pockets on the sides, as well as the three ones at the back plus the zip pocket, very handy when you have lots of stuff to carry and don't want to take a bag.

I use silk glove liners when it is really cold, with some Castellu winter gloves.  The liners are a tenner from Amazon, work brilliantly for me.

Legs - I use normal cycling shorts with leggings from Sports Direct that are about a tenner.  The benefit of these is you can use them off the bike, if you get hot you can take them off, and they dry quickly when they get wet.  I do have thermal bib longs too, a Castelli pair and a DHB pair.

Overshoes - Endura thermal ones are the warmest I have tried, and have lasted the longest too.  I would invest in some Northwave winter boots if I had to ride in the wet, a colleague has them and swears by them.

Mud guards!

Jacket: Gore Wear C3 Gore-Tex Active Jacket, or Gore Wear C3 Gore-Tex Paclite Hooded Jacket. I have the former and it's just a perfect jacket. Gore-tex, so will keep you dry whatever rain. C3 series: not race fit but a bit more space, ok for commute. Breaths well and also perfectly windproof (I find that in cold wind any Windstopper or similar material still lets some cold through). And I believe much more durable than the Shakedry, which to me seems good for emergency cases but will not last long with daily commute.

Boots: buy a pair of good second hand SPD winter mountain bike shoes. Quite some people selling them, many not much used. 

The most important thing is full mud-guards as they limit spray from the front and rear wheel.  Then a good jacket.  Winter boots are great. And full velotoze keep all water out (but sweat in)  Kind of agree with you that waterproof bibs are a bit illusive. Some of them are water repellent, but this washes off and is a pain to replace.  Assos Stormnuss are one solution - a cheaper I've been considering is cutting the legs of my old goretex trousers and using them as shorts over bids... If you don't have any old ones, get some from eBay...

I've two pairs of DHB bib tights, very warm, but not waterproof, but nothing on sale will keep out the water. I read on here that using a cut down pair of black rubber washing up gloves as gaiters will help stop the water going into your shoes. Neoprene shoe covers will keep your feet warm, but not necessarily dry if you don't stop the water running into your shoes.
Sealskinz socks will keep your feet dry, I've got some long calf length ones which resolves the water running down from your ankles, where most of the spray from the wheels gets you. But they are weird to wear.
I wear a Castelli Perfectto jacket with layers beneath, but it's not a thermal jacket.
One of my mates has a Galibier jacket which he rates, and I always mean to try their stuff it always gets good reviews.

Favourite cap, Madison Isoler merino wool cap, which I've lost somewhere, so I've got to buy a new one. Totally waterproof, as I use a Lazer O2 helmet with their clear plastic cover. Keeps the wind and rain out.
I use Aldi winter cycling gloves, which aren't waterproof, but are warm, but I don't suffer from cold hands, only cold feet. I started using those disposable chemical heatpads footbeds on cold days rides.

Another happy Galibier customer here, I use their padded tights and whilst I have better pads in shorts, they are easily ok for me up to about 60 km. The Mistral jacket is also excellent.

Good socks & overshoes are key. I have given up trying to stay 100% dry and now just want to be warm, hence neoprene gloves work very well (Endura). And always a buff.

Good thing about padless tights is you can get a few days wear out of them between washes, so you only need one or two pairs

I have padless bib tights made by giordana. Cost me twenty odd. Bargain.

Galibier.cc make some good padless bib tights for not a huge outlay, wear your padded shorts underneath and you'll have a head start in keeping legs and lower torso warm with the double layering. Keeping the top half is mainly about adding layers, something wind proof on the outermost layer and a thin waterproof thing you can keep in a pocket to deploy when required, adding stuff underneath as required. Anything truly waterproof gets a bit boil in the bag

Top priority is a good jacket. Lusso Aqua Repel gets good reviews but there are loads to choose from.

Add a good long-sleeve merino baselayer, I have Howies NBL and Endura BaaBaa.

Not sure many cycling tights will resist driving rain for long. Might make sense to have 2 cheaper ones such as Lusso Termico (review). Waist tights work fine for me.

Gloves: get good quality waterproof winter gloves. Liners can be a pain (EDZ merino are nice but a bit chunky, I tried silk but they didn't retain any warmth for me).

Plain neoprene overshoes will let the water through after a while so go for some with a waterproof layer.

Perhaps consider a 'Belgian' style winter cap that has a peak and covers the ears while a buff/snood is thin enough to fit under a helmet.

Have look in the road.cc review section for each garment type to pick out some good ones.

3/4 aren't winter kit - Spring Autumn - yes.

Lusso make some nice longs - they do one set that's reflective at any angle if you do anything at night.

Rutland had some longs from Caratti for £15 last week - tried them out yday in about 6 degrees yday and they were perfect. No need to spend £240.

Tops - LS merino base and a jacket over the top. DHB do a jacket thats great for this time of year - 

https://www.wiggle.co.uk/dhb-aeron-equinox-softshell/

It's wind and water resistant too.

If it gets colder then you can go to this jersey  - 

https://www.wiggle.co.uk/dhb-aeron-all-winter-softshell-jacket/

Some winters I've not needed it though - it really is warm.  The equinox gets more use and another LS underneath and you'll be toasty.

Rainjackets - then the SprayDry is the way to go.  Make sure it fits over your winter kit though. 

I don't think theres such a thing as waterproof longs - sure some might have a bit to begin with - but it washes off.   Make sure you have mudguards and at least your legs are keeping warm from the riding - they'll be damp but fine. 

Overshoes - Planet X do them for a tenner. SOrted.

Winter gloves - wooly ones are fine for now but you could do with waterproof ones for rain and thicker ones for cold - up to Lobster mitts for deep winter. 

If its that cold though - its prob icy so you might be better off training inside if you can. 

Flaps my sails a bit,
Yet a spray jacket and pants cover where I sit.
Cost 10 quid twenty year ago. 20 quid now.
Secret Santa bought me them and I know upper limit was 10 quid
Besides slow into wind they're great. Socks get wet though, no wind gets through, sweating at midnight mid winter isn't difficult. Totally dry besides sweat. Slow into headwind.
Although flappy, body warmth maintains bikes speed. Winter.. About 20kmph. Summer.. About 20kmph.. 20miles.. If your getting tail winds they'd work a treat.
Edit: 20 miles brings me smiles because I'm nowhere near them distances. Love ya work