Oh Dear @Nicnac12 That's a difficult one and your OH should have discussed this with you first, absolutely no question.
First of all, I think you need to find out how long they are planning on being in the UK. I think it would be reasonable for them to stay for maybe 3 nights with you while they are over here ( it's your OH's house as well as yours). Perhaps you could work from home using your bedroom for a day or two if necessary? Perhaps have them with you for a weekend, so that maybe only 1 day when you actually had to work from home?
I think, though, that your OH needs to get back in touch with his friend ASAP and say that they are still welcome to stay with you for said 3, or whatever, nights, but he has realised that it would be impractical for them to stay for the whole time they are in the UK as you work from home and that therefore there isn't suitable accommodation with you for more than that and also, he is sure that they won't want to stay so far out of London/will take ages for them to go in under their own steam and it isn't something either of you could do to help, due to work commitments for most of the days they are here.
In any case, even if they were wanting to stay longer, or your OH wants them to, neither of you are under any obligation to ferry them about. They just need to be aware how far out of London you actually are and are made aware, urgently, that they will have to make their own arrangements for sightseeing etc.
If OH won't do it, then I think you need to do it ASAP. Good Luck