Just came back from London 2w ago. Adultwork is a good choice, but I also just used Twitter and found couple independent ladies that I liked.
Have a look at this too: https://kinkylondonescorts.co.uk/
I was chatting with a SP yesterday about female condoms and she mentioned they are popular for duos. The ladies put them on and you can go bare and change with ease between them no need to pause to change condoms. Everybody is protected...
One more vote for female condom. I just discovered them this week and they are awesome. Nothing restricting you and no pausing to put one on...
But yes, they are not that popular, harder to find.