Thanks for the warning

Calling an unknown SP for an outcall in London is pretty much guaranteed to court disappointment.
Given parlours and spas are charging a minimum of 45ph in London, the chances of an outcall being cheaper are next to non-existent. Travel costs in London will add at least 10 (if they take public transport) and that's just the tickets, they'll be wanting to make something for the time taken for their roundtrip, so paying 60+ for 60 mins or more is not surprising.
If you have to get someone to come to you then hire someone you already know or is recommended by someone you trust or has a consistent recent record of credible reviews on UKP.