I can see that any sort of a 'shed' doesn't really work for motorbikes.
I also think that any sort of an issue (but especially mental health) means that you feel very concerned about change. You may well find a good GP surgery, and you don't say if your health is managed only by your GP or if you are seen by a mental health team.
You have 8 years, I think you said. We spent 5 years looking in a very concrete way at what we wanted.
You are not clear as to whether staying near friends / family etc. is important.
You obviously have to decide whether you remain important to each other, but assuming you do, I would suggest:
Begin now to look at places you might retire to. Go and stay for a few days, do activities there. Look at properties and do your sums (yes, I know inflation is an issue, but you have to start somewhere). Research local NHS services, and other activities that would interest you.
We found that the most important thing is to keep an open mind. As you look at properties and areas, say to each other 'where would the bikes go?', 'what groups could I join?' etc.etc. Doing this, being respectful of each other, enables ideas to come out into the open. It is easier to do this when you are not just fighting your own corner.
It may also be useful to think about what you want from a holiday - some folk just like seeing new places and doing new things, but if your desire is for some sort of break or change of routine, you may find it seems less important.
I wish you luck with all of it!