British slang for "being reassigned to the unsophisticated and remote regions or villages"

I am stumped in trying to remember the British expression used as a derogatory slant on being relegated, demoted, assigned to a lower position, reduced in rank, or (quite literally) being reassigned to the unsophisticated and remote regions or villages. I get stuck with "sent off to the 'colonies'," but I know colonies is not the term involved.

The term you are probably thinking of is "the provinces".

It is also common for London-centric people to use "provincial" in a pejorative manner.

Nowadays, generally when these words are used, it's in a knowing parody of that patronising big-city attitude, since people who live in "the provinces" are generally doing so by choice, and are happy to be doing so.

"The colonies" refers to overseas parts of the British Empire; Australia, Canada, pre-revolution America, various African countries, and so on. Being sent to the colonies would be quite a lot more severe than being sent to the provinces. Indeed, it was mostly convicts who were sent to the colonies.

Perhaps rusticate is the term you are searching for. It means to move into the country, and is used in some universities to mean being suspended for some time (made to move away from the university), so has most of the overtones you are looking for.

Perhaps

Sent into the sticks.

I have certainly heard that said a lot in the South East.