Finally up and running. Unfortunately, if I access GFN from my Xbox it does not recognise the controller as a valid input, even though I have enabled it in the Steam controller settings.
Oddly, if I connect the controller to my laptop, and run GFN from there, everything is ok.
Apart from not recognising B as the back button (even though it is mapped as such).
However, the mouse works well for selecting menu entries, so I can manage.
The graphics are a bit fuzzy (only signed up to the free access version), so I may have to look at upgrading to the next level in the New Year.