Hold light flashing

[briwy]

Coming back from the Northerners meet yesterday and the Hold light started flashing on and off without any apparent sequence, and not changing gear properly.
We stopped and and restarted and it cleared until we stopped again after about 50 miles in Buxton and then it played up again when restarting. Then cleared again. Not tried it again yet but it's obviously intermittent, possibly a bad connection somewhere.
This is a 2001 diesel with drive by wire so no info in the workshop manual or anywhere else I can find.
I have a suspicion it could be the TPS which I think is on the accelerator pedal rather than the fuel pump as on earlier ones.
I tried adjusting this last year and the Hold light started flashing so I returned it to it's previous position and all has been well until yesterday.
Has anyone got, or knows where to find, any definitive info on the drive by wire system and adjusting it?
Any other ideas anyone please, I know the speed sensor can sometimes do this as well, where is it?

edit, should mentioned ATF level looks OK and clen. I changed it cleaned out the filter last year so I don't think it's that.