Dear Autobox expert (if you exist)

My mk2 changes gear ever so smoothly, but from 1st to 2nd at 18mph and 2nd to 3rd at 37mph. Not good for town fuel economy.

Please tell me there is a simple 5 minute adjustment.

Changing fluid and adjusting kickdown had no effect.
Citroen dealer failed to get any code from the computer, Local transmission specialist read a fault code for throttle sensor, which has since reset after adjusting kickdown. He can't advise on the late change up though.

Any bright ideas?