Oily B2B Massage & Full Service
Oily B2B Massage is mainly provided by those who have never, or will never, provide Full service. Occasionally by someone that did provide Full service but has given up on that to retrain as a masseuse.
There are very few who want to provide both services or can provide them both competently.
The Polish girls based near Asda, e.g. Lovely Katie etc, and the Hungarian ladies based near Portland Square, e.g. Chloe etc, are well reviewed for B2B massage. £80 seems standard for their service. From memory, one of the Hungarians does provide FS.
Additionally, there are 2-3 English ladies who operate from St Pauls/St George, e.g. Bluesienna etc
Perhaps you should try some of those before obsessing on chasing the Holy Grail.