New Bike Advice - £1,000 C2W

With the Halfords scheme you can order off the Tredz website and use the full value i.e. your limit is £1000 not £900. They have a wide range of bikes including Giant, Cannondale, Cube and Scott with some great bikes around the £1000 mark. 

Remember you can haggle too - and I think you'd have a good chance of haggling now, with only 4 or 5 months left until the arrival of 2019 bikes. My C2W retailer didn't have the bike I wanted so I asked if they'd give me a good deal on a more expensive bike and bring it down to the £1000 C2W threshold. They agreed and so I ended up getting a £1400 Genesis Equilibrium through C2W

I'm with rdmp2 here. Tiagra 4700 is pretty decent and is basically a 10 speed 105 with slightly worse brakes and it's a bit heavier. I wouldn't prioritise replacing it until parts need replacing.

A new wheelset and some better tyres are far more worthwhile upgrades IMO.  

Have the commenters above used Tiagra 4700? Tiagra shifts really well, the only downsides are upgrade compatability with 11 speed (need to upgrade most of the groupset at the same time) and that you can only downshift 2 sprockets per shift. New Tiagra is really really good. The above bikes are either 11 speed 11-28 or 10 speed 10-28 so the Tiagra bike is only missing 50 x 11 (how often does anyone use that anyway) and both have the same gaps between sprockets

I'll be looking for a new winter bike that I'll hopefully get on the C2W scheme & have been looking at this:

https://www.dolan-bikes.com/road/road-bikes/road-bike-aluminium/dolan-rd...

Downside with Dolan is they charge an admin fee for C2W

If you want super value for money, the components on this are worth the 1k price and a surprisingly lovely carbon frame you won't go wrong with this particular PlanetX. I have the RTD90 and think its awesome, I ride a lot of long long miles and the frame is super compliant/comfortable. I know a couple of other quire serious long distance guys who have the 80 as well so its quite a recommendation. http://www.planetx.co.uk/i/q/CBPXRTD80RIV/planet-x-rtd-80-sram-rival-11-...

My advice would be to get the best components that you can immediately, you want to be looking to aim to upgrade the wheels down the line. As the other guy says don#t bother with Tiagra. SRAM Rival is the equivalent of Shimano 105

Buy the carbon one. 12 months later buy the alu one (or whatever version of alu the equivalent model is by then) and swap all the higher groupset stuff on to the carbon bike to jazz it up. That way you’ll have a freshened up best bike and a decent ‘winter’ bike, too. (Budget for new bar tape and cables.)

You could do it the other way round, but if you do that the 2019 carbon one will still have inferior kit and the alu may have upgraded to new 105. 

Dont want two road bikes? Buy the carbon one. Either way upgrade the brake calipers to 105 5800 ASAP. Don’t bother with Tiagra. 

Edit: the Tektro brake calipers are listed as ‘long arm’ so the 105 calipers may not be a straight swap after all. 

They're both top bikes and will do a grand job. I'd also lean towards the carbon one which has loads of potential to be a lovely machine if you upgrade some of the parts, only do that though when the original parts wear out. 

If you're looking for something a bit more versatile then I'd consider the CX Team Bike:

http://www.halfords.com/cycling/bikes/cyclocross-bikes/boardman-cx-team-...

Swap those tyres for some 30mm or 35mm Schwalbe G-One speeds and you'll end up with a bike nearly as fast as the above two but that can also handle the rough stuff. It's the perfect winter bike as it also has mudguard mounts. 

Getting a full SRAM 1x Rival groupset and hydralic braking system for £810 after BC discount is a huge bargain IMO.