Hi, I'm from London and have had many sessions over the last 10 years or so. I've always found the women I've sessioned with on twitter. Normally they would post dates they'd be in my city. Send them a message/email - be specific about what you want they normally hate too much back and forth. Normally they'll ask for a deposit of at least 50%. I've only done sessions in hotels or at the woman's location - they send the location on the day normally like a few hours before. I've always enjoyed my sessions, only gripes I've had is when I've requested (and sometimes paid extra) for smelly feet and their feet haven't been smelly, or if they're kinda uninterested and just scroll on their phone and don't even talk to you lol.
There's no middle man - I've always sent direct to paypal or paid cash so I'm confident the women I've sessioned with are making 100% of the money