Hey Pete,
Thanks so much for your support, it makes such a difference especially at my early stage of Flight Simming.
I thought it might have been the USB ports and have swapped between them but the problem has persisted. So no joy there.
Strangely I thought I'd go back to first principles this morning and started FSX without FSUIPC running and the throttle/mixture levers seem to be responding as normal. I've no idea why this might be although I've only limited confidence that it will continue that way! It's a bit disheartening as my Saitek Panel/Radio and Flight Switch boxes arrived yesterday and I haven't even bothered to unbox them until I can get some stability with what I have running at the moment.
Just to add another layer, I have to upgrade from Windows 7 to Win10 in the next week or so and I wonder if that will help or hinder. Maybe buy a whole new gaming PC (hahahahah!)
Cheers mate
Warwick