Make sure that the throttle cable is properly adjusted with a little slack to allow the arm to rest on the throttle stop at idle. My Rover 25 came to me with similar problems, I found that the throttle cable in previous ownership had been overtightened to get the revs up to try to mitigate a stalling problem from cold. I adjusted the throttle cable correctly and it solved everything bar the stalling problem which was more evident without the bodge of the overtightening. It took a T4 session to get the car running better and I think the base idle index is still in need of some attention but I hardly use the car and it runs in the main well enough for my needs for now. I hope to get it fully sorted in time but other things to sort keep getting in the way.
