Summit 1 - As more seasoned reviewers have mentioned many a time - and in my (limited) experience, massage providers offer a far more discretionary service than WGs.
Remember calling Adriana @ massagesme (Kensington & Chelsea, currently listed as on holiday). Rather than asking outright about services, just asked her to send me address / price structure and she texted back clearly listing btb option @ £110 - so I left the onus on the provider.
What followed was one of my more raunchier experiences.
Adriana is highly personable, Latin American, size 8-10, curvy, 36D (could be natural) and well toned. Highly professional massage for at least 10 mins, naked save for a thong (thats A, not me) , then BtB. As I reached to stroke her bum, she jumped off the massage table, cocked a leg and firmly pushed two of my fingers into her pussy. Followed up with RO, rimming as she bent over the table and finally HE and prostrate massage.
No idea if OW/ OWO is available as did not ask - what happened just flowed with no awkward questions.
No guarantee that this is the standard menu but i was more than happy.
Good luck in your search.