Okay, I finally looked up this bike:
http://www.cycle-world.co.uk/product...id=m1b0s6p6847

I don't know what price the bike shop is, but I think I'd recommend you avoid an 8 speed sora double.

If you end up upgrading the components on that... you're talking about a new set of shifters, a new cassette and possibly derailleurs... The price of which is going to be a lot.

I don't think I'd recommend you get less than a 9 speed double, and preferably a 10 speed... at least 105 level.

And I'd definitely look into used.