Just thought I'd give some input on stuff that's been said: as part of getting chartered you have to have some site experience and some design experience, so don't worry too much if you're choosing consultancy because you will be doing a secondment in contracting at some point. Another point to consider is that generally it seems that contracts get paid more early on and during internships, (partly owing to the higher work hours), but are limited in progression. Work hours can be pretty brutal, particularly if you work for a well known contractor whose name begins with 'L', but then again it's probably not as monotonous as office work.
If you're really split between contracting / consulting there are some in-house companies such as Skanska (although they're struggling at the moment) which might suit you better. On that note, Quest is having quite a lot of finanical difficulties, it used to be £3k a year, and the last final two years Quest haven't been able to meet that despite being contractually obliged to - I think there's probably a lack of public investment, but also companies such as Arup have withdrawn seen the majority of their Quest scholars leaving for finance upon graduation. I think this means it's gotten more competitive - at least that's what I've been told. At any rate, treat the company interviews as if you were interviewing for a graduate job. Good luck!