I think Cheshire companions may be of interest. They are the only agency I remember being posted about. I’ve never used them personally but thought a good starting point for you.
I could recommend CC, as I've used them a few times this year, prices still reasonable too -
but the 2 hour booking tho ideal for me might put people (as in the OP) off,
having said that their 2 hours @£240 compares well with some indie prices for 1hour!!