Thanks for responding to my questions OP.
You said 'We have had trips away together but we’re not really having much fun anymore. But maybe that’s what cancer does to a long term relationship?' I honestly don't think that this can be blamed on your illness, as I became disabled only a year after marrying my DH, he has to do so much for me, helps me to get dressed, gets all my meals, helps me wash when necessary, etc. We've now been married 28 years, and are still VERY happy together, in spite of the fact that I can't do nearly as much as he can. So it's not necessarily your illness, although possibly the way your DH has responded to it, which are two different things, if you see what I mean.
I think that sadly, many married couples drift apart over time, we all need our hobbies and separate interests, but it shouldn't be at the cost of our relationship, so it sounds to me like you need to have a serious conversation with your DH, and tell him that he's obsession with his hobbies, leaves you feeling lonely. If he brushes your feelings aside, then I'd be giving serious thought as to whether your marriage actually means as much to him now, or if it's just become a comfortable habit, and if it's a habit, it's clearly only keeping one of you happy, and that's not you. You may find that by developing your own hobbies that it fills the loneliness somewhat, but your comment about 'not really having much fun anymore', makes me think that perhaps you've lost interest in each other, and the relationship has run it's course.
One question you didn't answer is whether he has genuine reasons for now wanting to come back to the UK? I'd be interested to hear your answer to this.