http://www.myprotein.com is probably the cheapest and has the widest selection. There's a vegan blend, as well as separate rice, pea, hemp and soy proteins. If you use my referral code, you get 5% off your first order, I think: MP135271. They also price-match competitors and then discount it if you use the price match function. You can get some fairly good deals by playing myprotein, ironscience and Bulk Powders against each other using myprotein's price matcher. They used to have a sort of exploit that allowed you to stack discount codes, but sadly for me (and sensibly for them), they closed that little loophole (they once gave me a flat 20% discount code, which I used on top of price-beating discounts, and ended up getting about over third off of my entire order, which included 8kg of nut butters).
http://www.ironscience.co.uk/ has cheaper pea protein if you buy in bulk, though.
