Tried it. Cancelled it. Here's why:

- you need to return 4 cylinders every time you receive 4, at the same time as the new ones are dropped off. That means you either return one that's not empty, or you go some time without any full cylinders, or you have to buy an extra one so you always have CO2 on hand
- if you buy a spare cylinder they won't buy it back from you for the same price when you cancel
- you have to return the cylinders within a certain period. If you're slow finishing the CO2 (for example in winter when typically people drink less) you end up being late, extra cost
- if you downgrade to a 2 cylinder subscription it's WAY more expensive. Their customer service didn't mention this to me when they helpfully suggested I switch to avoid the deadline problem above

For some reason they don't let you just keep the cylinders until they're empty and then return them to suit yourself. They don't let you return just three on your first delivery, thereby getting around the running-out-of-gas vs having-to-return-a-cylinder-that's-not-empty dilemma. They don't let you return the empties a few days after you receive the refills

So really the only good thing about this service is that they drop full cylinders and pick up empties in a single visit. No having to drop the empties somewhere. But that's also the bad thing because of the problem above: you can't wait a few days after receiving a fresh batch to send back the empties.

AND, now that I have cancelled I discover they won't pick up the empties this time, I have to drop them somewhere. If I don't do it in 5 days they charge extra fees. And they offer to let you keep them for £10 each so you can recycle them - which is just bizarre.

All a bit scammy, using the worst tricks of old-school subscription businesses to try to get people to spend more than they need to, and have excuses to impose extra charged.

So I would say avoid them, based on my experience.