// It would be better if the UK economy, and safer for everyone, if we holidayed in the UK. //
I would venture that a UK holiday experience this year - for many - is going to be as out of reach as a foreign holiday.
at this time there are no projected opening dates for any part of the hospitality sector; when they are permitted to open, social distancing may well reduce capacity to the point where it would be uneconomic to reopen (maybe as low as a quarter capacity).
many attractions have not only been closed for 3 months, but have been locked out of bounds to all staff and in that time, staff competency may well have expired, maintenance will be out of date and electrical and load bearing equipment may well be out of certification. the following document sets out a recovery plan for tourist railways, but the same principle will apply to theme parks, and aspects of it will apply to many other leisure facilities.
https://orr.gov.uk/__data/assets/pdf_file/0010/42877/heritage-railway-recovery-plan-in-response-to-covid-19.pdf
pretty much all you'll be able to do on your holiday is walk or cycle - but not too far mind, as there are no toilet facilities, and take all your own food and drink.