I actually joined this forum to ask the question, so I'm glad I found this thread.
I should explain this is a new concept to me so I'm a bit shy. I choose Siam Orchid as it felt fairly genuine (so felt confident going in off the street), but with a hint of promise.
I called and booked a one hour massage from Dee, £30. Parking just further up, on the main road, about a 100 meter walk.
It's a nice place, very professional looking inside and a nice shower which I used before and after. There's a bit of road noise though and could hear people occasionally in the shop downstairs which is a bit of a mood killer.
Dee is mid-40's, not bad to look at. curly dark hair.
I entered the room and lay face down, towel still wrapped around my waist. She came in and laughed and undid the towel, lifted it and laid it across my bum.
She asked me to spread my legs a bit and started the massage. The towel came off after about 10 minutes. I was well aware that with my legs spread and her behind me, she could see everything hanging down.
At this point in my mind I was fairly sure this was more than a normal massage but being shy didn't want to ask.
I'd say about half the massage was rubbing my bum and upper thighs.
I turned over after 45 minutes (no attempt from her to cover my modesty). Then the towel scrunched down over my bits, lots of upper leg rubbing.
Then she massaged my head and that was it! She looked at me for a few seconds then turned on the lights and let me get dressed. I went to say something and she looked at me expectantly but I just said "that was great, thanks!"

I know now I missed my shot to ask, but genuinely wasn't sure if it was okay to, I thought it might be offered.
I'll definitely be back, the massage alone was well worth £30 - I've not really experienced anything like it.