Thank you so much everyone for all your responses so far! What a great community
Ok, I suppose I should give a few more details. The butane tank I have is a fairly decent size and I am in the UK (England) so refills are quite easy to get hold of and inexpensive. I have a torch which is a hothead-equivalent but as mentioned assembled specially by a guy in Germany, and it attaches with a hose and a pressure regulator which I also have (but for which I'll need to get an adapter if I'm going to use the butane). It's a surface-mix torch so I won't be using O2 at all.
You guys are being really helpful, I do appreciate it