The problem starts with (any) acft on the runway. Viewed from the back, whenever I move the mouse, the rear elevators goes crazy, moving up and down at a great rate of knots. Internally, the yokes go crazy moving in and out. If I don’t move the mouse, it does not happen. Using AP I can effect a departure (or sorts).

 So I substituted it for another mouse, Same problem as above.

 Next I tried the old trick of removing the Community file to another drive, then feeding it back a few items at a time, hoping to catch the errant file. 

Even with no Community file (I think MSFS creates a new one) it was the same problem.

 I have taken Addson linker back to square one, thinking maybe some file was faulty, but no luck there.

 MS2020 works perfectly, the aircraft are the same, even though the scenery graphics leave a little to be desired  !

That sounds very much like a control binding problem, did you check them to ensure you have no conflict between your mouse and yoke controls? There are a number of videos to help you for that like this one: 

 

 

It sounds as if, for some reason, the mouse is set up to control the yoke.

Go to the control settings in MSFS and check the assignments for the mouse. You'll probably find assignments for the elevator and aileron axes - delete those.

Control assignments in MSFS 2024 work a bit differently than in 2020, but there are lots of tutorials. Check out these two threads:

 

 

 

Thanks  Yes that was it. Many thanks for all your help.