mokryna Most houses in the UK are freehold. There has been a scandal recently because some developers were selling houses leasehold with escalating ground rents, but that is now being dealt with.
With flats it does vary. With house conversions into flats, the flat owners often own the freehold through a managment company where each flat owner has an equal share. Both my MiL and my sister owned flats that worked on that basis, while DS lived in a development where a developer collected the ground rent that could not be increased, but the management company was run by the flat owners.
In the past, in the UK, there was a prejudice against flats, but since the 1980s so many flats have been built that little of that prejudice still remains. However most of them are quite small and aimed at the first time buyer. You do get much larger flats in areas popular with older people, like along the coast, but these are not retirement developments
The problem with flats built specifically for older people in the UK is that they are so small, when up thread I compared them with rabbit hutches, it was for that reason. I used to volunteer with a charity for older people and visited a lot of people in such flats, and I was really horrified how small they were.
In France thing seem to be different. When we bought our French home the previous owner moved into a rented retirement flat owned by the local council. We visited her there and you could have got the whole of a McCarthy & Stone flat into the living room, and another into the bedroom and kitchen. It also had a small garden, much of the size you get with a small new build in the UK.