i got a pack of 7 vests from mothercare when DD was smaller and they were brilliant quality, washed brilliantly and didn't shrink in the tumble drier.
I've had a range of different makes of vests and they're all grand to be honest. Next were quite generous size wise but they all washed and tumble tried fairly well. My favourite was Marks & Spencers though.
Alwalys use mothercare vests on DS cos they are great quality. DS was born in Dec and loved the long sleeved options which I'm still using. Plus 7 in a pack is great - I find one pack does us until they shrink (after repeated washes) and then I buy them again. Highly recommend them.