I asked at the refdesk about private fostering here.
The only useful response was one Guardian article, and the writer and her expert didn't offer any depth upon googling. No academic studies.
Then I came across a scribble that I must have transcribed, probably from a R4 show: (Actress, born in London, raised in Hastings, 2 years Nigeria, back to Peckham.) Bola Akbajay, born c. 1980 Born Too Far (2007) In the early '80s, what a lot of African migrants would do, is they would take their kids to Hastings or nannies in places like that for the week, and then come and get us on the weekend, so for me, my earliest memory is being in Hastings, being on the beach.