I just did a search up in my usual stomping ground. The Nottingham - Chesterfield - Mansfield triangle. Compare search results today with what I remember 10 years ago and there's a big change. There are a lot more foreign girls. Especially Thai, Chinese, Brazilian etc. 10-15 years ago, foreign girls were almost always groups of Roms sharing a house while 'working' for Sergei. Just like the Romanian girls, the current crop of Chinese and Brazilian SPs seem to move around the country, so there's usually a few new faces each time you look. There are fewer young Brit girls still to be found but the majority of the 'local talent' looks to be chubby middle aged housewives charging far too much for a very limited likes list.
I think lockdowns and the credit crunch hit hard. Girls found other jobs to pay the bills and haven't come back. When demand picked up again, foreign girls flocked in to fill the gap.
It'll all change again. It always does. Eventually, more new UK girls will get established. It'll take time though.