New bike

You could also consult road.cc's list of the best £500-£900 bikes:

http://road.cc/content/buyers-guide/71216-best-£500-£900-road-bikes

Well you're looking at the right time, since the end of season sales are starting to kick in. I'd look for something around £800, then watch for the reductions. Think Evans have started, Cycle Surgery will be soon etc...

Merlin cycle store- Sensa Umbria sora at £510.enough left in budget to buy some look keo pedals at half price £24.then sell wheels on new bike and put a bit of money to the sale to buy some lighter wheels

Nothing wrong with brands sold in halfords or Evans, in fact that's where I'd look with £600 to spend...

Otherwise I think you'd be better off getting 2nd hand if you want something more unique

Visit some shops and see what that have that fits and takes your fancy. All bikes are great nowadays, you're spoilt for choice.

Giant Defy would be my choice.

I was in a similar position recently. My lbs stock mostly Trek Cannondale and Giant and reckoned there was very little between them. They did reckon the Giant Defy 3 was on balance the best bet, although IIRC was around £650...haggle?

I eventually bought a used Bianchi Nirone 7 because they have good reviews and more importantly look fantastic....probably as good a reason as anything at this price point. After overcoming a few niggles I now love it