With regards to St Hilda's...I live there and love it! I'm going back for my third year next year...if you're from a small town you'll fit in well, since we're mainly country students (as opposed to say, Trinity or Ormond which have a high proportion of city kids). We have an awesome social life - there are official events nearly every Wednesday, and we head to the pub on a couple of other nights most weeks - that said all colleges have great social scenes. Mary's is also a great college, however be warned with Newman that their head of college is EXTREMELY strict.
About tutorials: all colleges have tutes, and if they don't have one for your subject, you can always go to a tute at another college. That said I reckon college tutes are overrated...