We've used 901s for a while with our Camping Gaz BBQ. They've lasted a lot longer than 4 BBQs, but they're difficult to get in UK. We bought our first in France a few years back, and most big supermarkets have them.
Interesting experience which might help others in similar situations - this July we changed an empty 901 for a full one in a Casino supermarket in Cahors merely by taking the empty into the store, collecting a full one and presenting both at the till. This is what I'd done with 901s and 907s in France for years without any problems, but when I tried this in a Casino in Durkirk on the way back, I was stopped not long after I'd entered the store by a security man, who shouted at me in a torrent of French (no kidding!) and when I said I didn't understand, summoned another TWO security men who demanded I came with them - a bit scary being marched off between three heavies! I was taken to an office where a woman took my empty 901 and gave me a chit to present at the till when getting the new one. All done in a very unfriendly and brusqe way, and my observation that this wasn't usual practice and there were no notices was treated with contempt. French bureaucracy at its absolute worst! :crazy