What kit do I wear when the weather is on the turn??

I’ve got a pair of (non

I’ve got a pair of (non-cycling) Columbus Sportswear windproof gloves that are perfect for this sort of weather. They have a reflective foil lining, palm and finger grippers, and you can use smartphones with them. And on sale at the moment:
https://www.columbiasportswear.co.uk/mens-trail-summit-running-gloves-1749501.html

Pretty much what everyone

Pretty much what everyone else has said.  A pocket-sized gilet is the most useful piece of clothing, plus  LS baselayer (I can pull the sleeves up if need be), ordinary jersey, arm warmers, and either bib shorts and knee warmers, or calf length bibs from Decathlon (the former if it’s going to be warm on the way home).  Arm warmers and gilet usually get removed at about the 20 minute mark (after a big descent, which is always a delight last thing on the way home)

Still in shorts at present

Still in shorts at present and short sleeves though this is with arm warmers some days and have added a mesh base layer. Will make the switch to full sleeves in November along with knee warmers or 3/4 bibs, this also means swapping the drawers around. My kit is divided into winter and summer drawers.

Met Office.gov.uk local

Met Office.gov.uk local forecast the night before and, if unsure, a morning check of the latest Met Office readings from the local weather station (about 2 miles from my workplace). I prefer to put up with feeling a bit brrr! for the first mile or so because I find it much more tolerable than being too hot by half way.

11-15°C normal jersey with arm warmers and either knee warmers or 3/4 tights;

< 11°C lightweight windproof jacket, cycling cap (easily removed once warm);

Below about 8°C long sleeve merino baselayer under the jacket and full length tights.

For your start I’d perhaps a gilet might be worth a try. A 5p carrier bag under the jersey or jacket is an emergency/cheapskate way of keeping cold air off your chest.

I’d agree with start cold and

I’d agree with start cold and warm up.  It can take 3 or 4 miles before my hands get comfortable.

Another one for Castelli, I’ve pretty much fine tuned my setup now, although I do tend to run hot. I just open the zip to cool down if I’m in a windproof.

• cold ish and damp Gabba, endura baabaa ss and arm warmers, omloop thermal bibs (high single digits) 
• dry, swap for an alpha wind jersey (today) or a LS stolen goat (not windproof)
• colder and wet or dry Perfetto and ss baabaa, sorpasso 3/4 (low single digits) Planet X 365 gloves
• cold and wet or dry Perfetto, full length sorpasso and LS baabaa (very low single digits to zero) same gloves.  On a long ride (200k) in these conditions I used a pave waterproof and a LS stolen goat as I knew a gabba or alpha would wet out.
• very cold, full length sorpasso and alpha jacket with ss baabaa (down to -7 so far) warmer gloves.

Always Shimano goretex mtb shoes with merino socks and endura overshoes.

There’s quite a lot of overlap in the comfortable temperatures for these, so it generally works well enough.

Tights for the first time

Tights for the first time since April this morning… plus a 20yr old Assos windblock jacket that won[t die.  They’re all set out for tomorrow morning’s ride too.  With overshoes.  It’s cold at 5am…

Never tried the Castelli

Never tried the Castelli stuff (Gabba/Perfetto) but I have a Gore Windstopper jersey and love it. It’s short sleeve and in that and with a pair of arm warmers (mine are sportful no rain, which like the jersey are good in light rain as well and feel windproof) I’ve ridden in temperatures between 4 degrees to late teens.

Choice of shorts/tights, gloves and potentially base layers to fine tune to taste and stick a packable softshell/gilet in the back pocket to cover a LOT of grounds! Works for me, anyway 🙂

Just bib shorts and shoes,

Just bib shorts and shoes, nothing else.  Don’t go outside on UK roads from September till April.  Conservatory is my road and this