Because of the 90 day rule, which has been mentioned by others above, you will either have to spend a large part of the winter in the UK (or Ireland or some other equally cold part of non-Schengen Europe) or take the Morocco option that others have mentioned. The latter creates health
insurance problems, because most companies either will not let you spend more than 3 months at a time out of the UK or charge a very high premium to do so. If you take the Morocco option, you need to research the health
insurance angle very carefully - it could leave a hefty dent in your budget. The same could well be true of vehicle
insurance, so check with your insurer.
One further point about the Morocco option - don't stretch the time limits to the maximum. If you spend 90 days in the Schengen zone and then go to Morocco for 90 days (the maximum you are allowed there without a visa) then the times are critical. Miss your ferry by a day and the authorities could get very rigid about it - especially if it is the Moroccan authorities. 91 days in Morocco could lead to a major fine and confiscation of your vehicle. I would advise that you spend, for example, two and a half months in the Schengen zone, then just under 3 months in Morocco - this gives you flexibility at both ends.
If you decide to spend part or all of the winter in the UK, then bear in mind that a lot of campsites will be closed. Also, basic things like laundry and getting your towels dry can be a pain. In a house, drying a towel after a shower is no problem but in a motorhome, where damp is the bane of many lives, a wet towel can be a major problem. Not insurmountable but you have to think of the little things that didn't concern you before.
We have been "most-timing" since 2002. We have a house but my sister lives in it full time and we spend no more than a month a year in it (although that may well change if we aren't allowed to travel for some time because of Covid 19). Up to now we have had the freedom to travel around Europe at will but it is going to need a lot more careful planning in the future because of leaving the EU. However, we do hope to continue. It is a great life and whatever you decide, I wish you luck in your new life.