The dinky "handbag" size (3.9kg) propane cylinders aren't bad for convenience or price; the valves on them are better than any of the disposables and they're much less likely to leak. I've had a few disposables empty because the pin valve stopped closing properly.
Your break-even point is pretty good too - a quick check online shows a deposit (only partially refundable - which is probably why you see so many at tips) of £35 and a refill charge of about £15 - given the Bernzomatic-style canisters are £10ish each, you don't have to go through many before you're ahead of the game with a proper cylinder.