What a fascinating post Shona.
During my lifetime, my aunt and uncle were housekeeper/cook/secretary and chauffeur/general handyman to the widow of a multi-millionaire who had a large "wedding cake" type house just behind Kensington Palace in London and a country estate in Hampshire. By this time (1940s,50s and 60s), they were the only full time staff she employed. Most of the time was spent in London where my aunt and uncle had a flat in the basement of the Kensington house - somewhere I remember staying many times as a child and a teenager. At the time, I thought ALL Londoners lived in such houses on such a street.
My sister often stayed with them in their estate cottage in Hampshire before and during the war.
Mrs.X was a pretty good employer I think (she always gave me half a crown when I stayed in London as a child - which was quite a heady amount of money to a 1950s 6 or 7 year old!). When my aunt and uncle retired, she bought them a bungalow on the south coast and also left them something in her will.