Jon / Trevor, thanks for the response -
So last night I did go and give it a wipe, and the problem improved, i.e. it did not go away entirely, the system still selected options on the touchscreen by itself.
Then I gave it a really good wipe, and the problem did go away for the remainder of my journey (15 mins).
However this morning, with a spotlessly clean touchscreen, the problem has returned. Devastated to say the least.
I'm wondering could there be an issue with something behind the screen, because for sure the wipe I gave it last night definitely improved things ?
I'm also tempted to to a battery disconnect/reconnect, would that be worth a try ?
Cheers, Paul