Firstly lets well define the market & divide it into two main sectors:

1- The wealthiest people allover the world who have the potential to buy castles and villas with millions of pounds in the means of hedonism more than trying to make more money.

2-Wealthy people but not as the above ones who will be very aware of spending money and always searching for reliable benefits which affordable cost.

For the first market sector: I would suggest creating a yearly classy event for all international huge properties' owners. All business people, political / governmental and media leaders in the UK should be invited. The main purpose for the event is to choose the best and most luxurious property, the property owner will be then the main guest of the event & he can afforded the British nationality as a prize. Using media in spreading such event allover the world can encourage wealthy business people already existing in the UK or not existing to search for the most expensive castles in the UK trying to feed their hedonism.

For the second market sector: I would suggest that the governments in the UK would take advantage of the amazing reputation of the British educational system, they can encourage such people to come and invest here by buying properties for few hundred thousand pounds & in reward offer them and their kids the chance of joining the British schools and universities with the same fees of home students.

If you would like any or both ideas, I can explain more why I have thought about them according to my experience being studying project management in the UK. Also, being living in the UK and Egypt my home country where I used to deal with a lot of people who owned the idea of buying properties here in the UK.

Thanks,

Ahmed