Brexit absolutely is the reason the Poles and Hungarians have either gone home to their paid for houses and seeded businesses or property portfolios and improving economies or naturalised into the citizenry and gotten regular jobs having bought a place here with their earnings and settled their families here. Fuck it even cleaners are getting 20 quid an hour and if some happen to turn a trick or two for some overly generous letches then they're set. The exchange rate would have to move to 1.3+ Euro to make some more consider coming back, probably all would be flitting rather than coming to stay since they could command a premium for being less available and I doubt we'd see much of the young hotties, more like the slightly worn but experienced SPs of recent years re-stomping their grounds and perhaps doing more touring of the Isles rather than any residencies in London.
The SPs who remained before CoVID weren't driven back into the game by the loss of labour and income from other employment so they're either well integrated and claiming benefits as citizens or else back home without rent to pay or just tiny mortgages.
I haven't been watching what's happening in the regions but there hasn't been much cheering for the return of our favoured nationalities to the broken bedsprings in the parlours and flats.
The "Brazilians" aka Spanish and South Americans are here because of trafficking by gangs who spot the opportunity of blueballs up and down the country hankering after Thai, Pole and other developed-EE girls and taking any rent-a-puss in lieu. Sure there are also some enterprising lookers of dubious original gender who make their own way here from their bases in Spain (perhaps bought from previous heyday proceeds). Their home economies are all tanked so the UK scene is primed for exploitation. As our paying the 20%+ increase in base fees and ridiculous extras confirms.
Talking to some of the older Thais who are still plying the massage tables, they're also doing other jobs, some are cleaning and their clients are former punters who want exclusive access to extras after they've done the chores. It's not exactly SA in the SB sense, they're after sex slaves.