Hi Malcolm, yes Ethanol is very likely to be the cause or at least an aggravating factor, and things are only going to get worse for all of us in years to come (I am starting to see more and more and new/different issues on a lot of carburettor work I do and 99.9% of it is due to fuel and ethanol contents.....)
Unfortunately if you take the car off for that long you will be more likely to face these issues. So 1st things first, run the car regularly even during winter times, there is no substitute for it (and it is not only your engine and fuel that will thank you for it...)
Then need to look around you for petrol stations with E5. I know this is stating the obvious but only real way to go about it TBH.
I know people talk about some additives etc but not had first hand experience of them (and dont really trust most of these TBH as usually design as stop-gap to cover an array of vehicles but never really engineered for a specific engine/car...)
Good luck (and welcome back to the UK)
Geometry Dash