I had what sounds like a similar problem a while back.

After advice from the Forum I cleaned out the Idle Control Valve (Rimmers do a kit with new plastic bits and a gasket, about £12 I think), but it did not solve the problem. It turned out to be a simple mechanical issue with the plastic thingy on the end of the throttle cable sticking a bit and not releasing properly at idle, which was why the problem seemed to clear with a throttle pedal blip.

Anyway, read all about it here, especially Post #15

https://the75andztclub.co.uk/forum/s...d.php?t=302496

We finally got round to fitting a new throttle body today. And Banana drove home without over revving once. And I came home through Newton Abbot town centre, so plenty of stop/starting. And once onto the A38 I wound the elastic band up and cruised home at Warp Factor Three and a bit.

Well pleased with the work carried out by Matt Darke aka Cable Tie.

after much faffing about with my old throttle body with gasket idler sets / cleaning etc. i bought a new one which was on offer from brown/gammons. went down there and picked it up. boss there told me it would need to be "introduced" to the E.C.U . mechanic said it was good to go. took my chances and fitted it myself with a new manifold to throttle body gasket two days later. never a problem since ... ;)

david75 has a point with very worn throttle body linkages. i do know which slider he refers to. its the white plastic coloured one in the "arc" slider at the side , where the spring is attached . they develop a lip / groove on themselves and stick if not cleaned out . lubrication only attracts dust and grime but a clean out might sort it if not too badly worn. for the cheap price i paid for an on offer part which included map and idler valve it was a no brainer. .. :D