Small update.
After some teething troubles with the carbs (I've swapped form 34ICTs to 36IDFs) my Nova is once again mobile under its own steam. I took it for a loop round the block, so I could point it nose down in the drive, and it performed well. The hard starting problem seems to have been cured, at least.
I can now focus on more tasks to bring it back up to an MOT-able state