I have an original vodafone dongle (3G),
http://shop.vodafone.co.uk/shop/deal...up-and-go-blue
these used to be everlasting (almost) but have changed to 30days then top up at £15...(ouch)...but you can get the old sims on ebay (300391396975), or other sims if you can get it unlocked, 3's seem cheap, search for data sim.
also the E220's can be picked up unlocked on ebay, may have faster speeds, (120569580654), see what Truman uses.