Thanks, Tom.
I thought about doing that but it's just such a pain in the ass, sorting it out and paying for it...!
I know how to do the actual filling and I know the safety drills - I'm an ex-welder and the equipment is the same.
I live about a mile away from Planet and they'd done some fills for me a few years ago. It's a real bind that they've stopped this service.
But jeez, all I wanted was some refills so I could take the kids target shooting... *sigh*