well tbh everything is upgradeable!!!lol ,id say get a bike with a good frame and forks as a starting point cos in reality youl prob want to change all the rest .
there is loadsa choice but personally id b looking at something second hand or even buy an older style road bike and convert it if u like tinkering (and they look really good) ,if ur going pre built then most bigger names have a ss offering in their range ,its just finding one at the right money ,no reccs as in "buy this,,,
"what i would say is dont limit yourself ,you may have to travel to get a bargain ,,as opposed to buying blind i think ul b very lucky to find exactly what u want and try before you buy ,unless you spend a good bit more and buy brand new from evans or such ,,,take ur pic"