I’d go Affiliate Future. The others mentioned (CJ, Paid On Results, Awin, Tradedoubler etc) have a hefty set up fee (up to £5000), which has to be recouped from your sales.
Affiliate Future is only £750 I think. They also have a good rep in the industry.
if you want more info i can always get you in contact with the top guys there. pm me and i’ll set you up with msn addresses for them and you can have a chat.