It's been a long time since I made any progress, partly down to doubts about certain things on the kart, partly to do with health issues, both mine and Mams.
Health problems seem to have been resolved, mine entirely, Mams as much as they're going to be, considering she's 98.
One of the main doubts I had with the kart was the spongy. ineffective drum brake. I found myself wishing I'd gone for a disc braked one, so I did a bit of research, and realised I could fit a rear disc brake. So I've bought a wheel from another model of the same make, and I can use the caliper off the front of the scooter. I'll probably have to add a plate to the rear of the outboard bearing mount (bolt on swinging arm half), but that's easily done. The new wheel also has a drum, so I can use that for the handbrake.
Once that's sorted I'll get on with the front suspension and steering rework, not setting any firm target, let's just say Spring next year.