Sorry to be an advertising whore, but depending on your size, this may help.
eBay.co.uk: Otter Britannic Drysuit (item 190123571122 end time 25-Jun-07 20:00:00 BST).
Yes i know its blatant but if not your size i do appologise.
But helps to answer your question. Go for membrane, and a good quality one it will last eons.