Oh yes!

[RDGAC]

Hello Rick - in fairness, I live towards the opposite end of the country (York's about 200 miles away from Brighton), and it costs a goodly amount to cover the distance; I'm not sure I'd be of too much use.

I've pulled the lock apart as far as I can (quick squirt of WD40 seems to have been enough to slacken the screws, the mainspring's excepted) and can't see any obvious means of detaching the tumbler from the hammer from within. There's a further problem: the barrel tang screw is attached to the sling swivel by a bent iron spike, which looks very unlikely to respond well to being pulled, pushed, hammered etc. Meanwhile, the bottom (or, depending on PoV, the top) of the screw has been hammered flat, and spread accordingly; this is presumably intended to stop the screw from slipping through, as it's likely worn its threads right out. This likely means dismounting the barrel is going to be a tricky proposition.

One obvious (but invasive) solution would be to file away the flattened-out edges of the screw and simply pull the whole assembly out; then, assuming I can find an appropriate die nut, gently freshen up the threads a bit and see if they'll then grip the hole in the tang. If that fails, I can then replace the screw and, mounting the gun correctly, gently hammer the screw's head until it spreads enough to be held in place again. Any thoughts, chaps?