im getting one myself next week.. but TBH i'm just buying new... the second hand value of ipads is far too high.. you pay £250 for a 1st gen ipad, and you'll end up paying £350 for a 16gb wifi ipad 2 on the second hand market.
for the sake of £50, i'd rather have the warranty and be able to unbox it myself
Students get a 20% discount on apple products. you have to connect to the apple store through your university network to access it so this might be a route to cheap apple stuff.