I could be wrong, but the jewellers torches I have come across, besides the handheld butane ones, have been oxy/propane, using 2 tanks or just propane with airflow adjusted on the torch itself, perhaps it's a UK thing?
Acetylene seems to be reserved more for large workshops. The only oxy/acetylene torch I've experience with was cutting metal in a foundry.
The other issue with acetylene over here is sourcing it could be a headache, and oxygen tanks too whereas propane is widely available. Not sure where your home insurance would stand either having oxy/acetylene in the house, that is of course only if you are working at home.
Fionnghuala, if you are just doing small pieces I think I would stick to a butane, sounds like the adjustment slider on the side of your max flame may be stuck on low, so if you can't fix it a new one may be in order. But if you want to experiment with techniques such as fusing copper or brass, and casting, then I would go ahead and have a peek at the two torches I mentioned in my first post. Hope that helps.