Colin, if you have found a caretaker that will use your sevices your very lucky, cos they usually say "oh the cleaners do it daily", obviously not the same as a professional clean.
I have been doimg a bit over last year, and yes it can be lucrative, find them in all sorts of houses, mostly in top end houses that can pay.
Just looked at a new floor to clean prior to sealing, being Cumbrian yourself will know about Borrowdale slate tiles, bloody thick uneven things, only difficulty will be uplifting the slurry

Andrew