The Post Office do quite a decent roll for �1.00 or you could try The Pound Shop if you have one locally.
Garden centres also do it, their's is the larger bubble type, they sell it by the meter.
grannyg
I have moved a lot of times and the best places to buy a load of bubble wrap are self-storage units or removal companies that do self stroage. Cartons and tape are also cheaper in these places.