I did a fashion shoot at Longleat House last summer, but that was arranged through a personal friend of Lord Bath, so not really an option for you. You could try Lordship Park, but it's expensive - around £400 per day if I recall correctly. Sorry can't help with the jet. I suggest you try a few private airfields or private charter companies.
There are loads of location companies out there that will be able to source this for you.
Plus there are plenty of houses out there that can be rented or used. Sometimes hotels, clubs, restaurants etc. will let you use the locations for free as long as you give them some publicity, but from experience they'll not even speak to you or discuss it unless you are a high quality professional photographer with lots of previous experience and credentials.
They want publicity, but they don't want bad publicity and crap, amateur photos posted on social media with blurb describing how they shot there and did this and that is most definitely bad publicity.
Too many venue have been burnt like this in the past. If we ever use a junior behind the scenes photographer we have to have a very tight contract that they won't use the photos.