"A play about a downtrodden housewife who worked as a daily help in a middle-class household was made by the BBC in the early 1970s, and was repeated a couple of years ago. It was set in the Manchester area - in one scene, the leading character disembarks from a half-cab vehicle in SELNEC livery, which I think may have been an ex-Salford Daimler. Ben Kingsley had a small part as an employee in a taxi firm." (thanks Alan Sinclair).
This was one of the Play For Today series and was made by Mike Leigh in 1973. It also starred Alison Steadman and Liz Smith.