Go to the Dollar Store (or whatever they have in Wales) and get one of those "super-grip" things you use to open up bottles.

Or

Hold the lighter to it. That would heat it up faster than hot water, but be careful, sometimes it will burn ya'.

Or

Smoke a bowl out of it. It's easier to get the bowl off right after you smoke.

The Super-grip Bottle Opener (You know, those little green pads) is pretty strong. Combine that with a little heat.