Cambridge Parties might be good. Solid review record, and girls' service can be confirmed based on their own reviews. Although I'm not keen on punting in a room of other guys, it could fit the need for others. You could potentially fuck up to 5 girls for £220 (£44 each), and an hourly rate of £110ph.
Not been to a Cambridge Party, and they might be different, but I've done plenty of parties in London (like Rebecca's, Phoenix, LAPC), Bristol, Birmingham and elsewhere. They tend to be a "hello, spitroast (blowjob, then swap and fuck), next please" production line. No real engagement with the girls, or only a little at the end if you last until most of the other punters have left. Not much banter with the men either, unless you've seen them round a lot. It's fun if the organisers are filming a mass bang or bukkake session, though that's rare, as it sort of heightens the buzz. But in general parties tend to be emotionally unsatisfying. Just getting your numbers up doesn't do much for me. I much prefer a 1:1 cuddle, natural sex and chat with a nice girl I know who has time for her clients and interest in them.
London's big, and I've never run into someone I recognise. And I'm sure both sides would stay shtum if they did. Parties also tend to attract a lot of tourists for some reason, and of course you don't know them. So running into someone you know is maybe not a real worry even in little Cambridge, and seeing other guys bonking away can be fun too, like being in a porn film.
I think parties are something you have to try once and see how you feel. Some guys seem to go over and over again!