The best I've had for this (and I've had the likes of Maria of Edgware and Lola Bell) was 999Sarah999 (her AW name), Lola's erstwhile flatmate in Earl's Court. Sarah's profile is down, presumably because she is in Hungary but she has gone home and come back a couple of times, so keep an eye out. She may appear at some point in the future in a cheaply furnished flat near you.
One other option is Lithuanian Sandra who works out of Temple Fortune, just north of Golders Green (no AW profile but Gumtree or similar might turn her up). Both are around £60 an hour for naked massage and excellent HE. Saw Sandra about three years ago and Sarah about two years ago. A third option is Lucy blonde Pole in her 30s who works out of a TCM in Bromley, though she may well try and upsell you to FS. All three excellent at 'edging'. She's also damned hard to fix an appointment with as she only works a day or two a week.