Hi Brian,
Your thread has raised several good points about inverters but, from your last comment:-
Ta for the advice,Mark, looks like I need to retrain my left hand to use the push and twist switch instead of the speedy wheel,what a pain
that sounds like you don't have an actual Run/Stop switch. A 'Twist to set/push to release' switch is normally used as an Emergency stop, as all you have to do is 'hit' it. Emergency stop should be wired to its own input on the inverter, and a separate Run switch wired to that input, to purely control the motor. If that is not the case with yours, may I suggest you ask your friend to add one.
By the way, I would concur with other posters that using the pot to start/stop the motor is not advisable for the reasons I gave in my earlier reply to you, namely the motor may still have power to it, even though it isn't turning.
Hope all this chat about inverters etc. isn't keeping you from your turning