I fitted the rear arm to the white BX last night, so that's no longer leaning. Just the cambelt to do and it'll be finished, or ready for an MOT at least. I thought that by buying something which had just failed the MOT would give me a clear picture of what work was needed before buying - not realising that 'just' meant 3 years ago...
And I might have an idea for a quick summer project

A new engine for the mower! The engine it currently has dates from the 60s, and while parts are still available plus the engine itself is in good order, it's always difficult to start after the winter. There's something amiss with the ignition system which I just can't work out, and finding advice on magneto systems is less easy nowadays. Plus it can snatch your arm quite painfully when starting it with the pull cord.
While I was down at the agricultural/engineering suppliers yesterday I was chatting to the owner and it turned out they have a Honda diesel engine round the back from a failed generator. 9 bhp so slightly more power, I can run it on red diesel so cheaper to fuel, but the big plus point is that it's electric start. Just need to measure up whether it will fit...