As far as I am aware....
London & Manchester are the top two cities, both have parlours, agencies & indies galore!
Leeds have good agencies & a sizeable number of indies. Not aware of any parlours there?
Birmingham has several parlours (not much talk of them in the cyber world though?), few agencies & a sizeable number of indies.
Brighton has a decent number of indies, a couple of agencies and one very well known parlour (are there any others?).
Hull has several parlours, some also provide outcalls. Not aware of any agencies and not many indies.
Milton Keynes has a handful of parlours, only aware of two escort agencies and a very small number of indies.
Nottingham has a handful of agencies and a decent number of indies. Only aware of one parlour, which doesn't appeal to me, I think they only do massages & HR like ego in MK.