I wear a sports bra under my trisuit even though I've not got much to put in it, usually a Sportsjock one but Little Miss Happy has it right, they do take ages to dry out.
I prefer a one piece suit myself as it keeps my fat belly under control a bit better, although going to the loo can be a pain!
Start Fitness are quite good for cheaper stuff. Got a Scott Trisuit from there that was around £25 or so and it's great.