The Samba's been to the garage. The brakes were soft because ... the calipers were siezed and the hoses broken.
Plus a few other things like CV boots needing replacing, washer pump inop and front suspension legs corroded.
I was right to be concerned that the seller was also the MOT tester, but there's probably very little I can do about it now.
On the upside, the engine's fine and hood's almost as new, although the bodywork is starting to go at the edges - I can get this done easily.
David :-(