In reply to TobyA:
> You are really angry with them aren't you!
Oh yes! That's what happens when you blow your second chance. Still it's their problem, not mine. Any number of decent bike shops out there.
Anyway, for the OP, I find myself in a position of being able to comment with a fair degree of insight on carbon, aluminium, stainless steel and steel, as follows:
Aluminium - nice to ride - no vices and tough. Light. Happy with a significant coating of gunge and grime.
Steel - heavier (in my case), comfortable, tough as old boots, workhorse with mudguards and rack. Resistant to significant neglect
Carbon - stupid light, aero frame, stiff as a slab of armour plate. Bone-shaking, but a different frame design would give different qualities - choose with care, with particular regard to the seat stays I would suggest if you're after comfort. I reckon you could poke a pencil through the side of the big aero down tube. Bit of a pretty boy when it comes to maintenance and care, doesn't like grit and stuff.
Stainless steel - tough, light, stiff but absorbs all the bumps. Too good-looking to hide behind grime, but shrugs off anything.
Horses for courses - of all of the above, the stainless steel one is the keeper. Frame costs for the carbon and Stainless ones were about the same. The alloy one is an old Trek Discovery Channel for £350 off Gumtree, and the steel one was £650 about 8 years ago (it's a fixie).
If you want something to withstand a few knocks - I'd go steel, alloy, carbon. Mind you if you get the wrong knock on any of them, it won't go well. Carbon is the least able to withstand abrasion, but it's also repairable at a very reasonable cost if you know the right people
http://www.carbonbikerepair.co.uk/ - One of their demo bikes is a TT bike that had been run over by a tipper truck and you'd never know.