Just to fill in a bit more info I had a very unusual problem where my gearbox got stuck in 2nd gear. I contacted the suppliers in the UK and they advised me to remove the remote on top of the gearbox. Unfortunately the problem was not in the remote and the gearbox had to come out.
Here are some photos of the remote on a Plus 4.

The actuating mechanism which goes where the lever normally sits.

Opened for inspection.


As I could not get the cover off I had to work through this hole in the top and reaching under the sides of the cover whilst it was propped up at an angle.