It isn't that simple:
Retire state pension + 2k a month - They still need a pension pot of nearly £500,000 So post Brexit only applies to 12% of UK retirees.
Work. 45k. - need a definite job offer. So will need to speak the lingo, and have the required skillset. So very specific to the individual.
There was no such restrictions pre Brexit.
Study. 6k + an acceptance letter. plus health insurance and proven accommodation. And must pay international student teaching fees.
Easily available in all students reach.