I have fond memories of camping around there when I was younger. We used to contact the local churches and get them to introduce us to parishioners with land and more often than not we’d come up trumps. I appreciate this is not a conventional route but it is perhaps worth a try.
I do this with my camper van look for farms near where I want to be or on route then just give them a ring or email if you can find one. The farms that do b&b are normally the most accommodating
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.