Thanks all.
Used him for a few things - v good, but he's not doing so much on the fixing front these days. More parts supplier. Pity.
@Brown I'll try the purge cycle again. Don't have an diagnostic kit to try unfortunately.
Try the easiest thing first charge your battery or replace it for a heavy duty truck battery, TD5's require a good battery to spin them over fast enough to start in cold weather, once started they are fine, classic battery issue.
Hello again all. It's been a while for several reasons but I've an update (in case anyone is interested :)). So:
1. I have, I think, resolved the first problem (starter intermittently clicks but doesn't engage) by fitting the Fourby solenoid...