Hi,
I am also type IV and have had treatments at RM Oxford Circus.
You can read about my experience in the link in my sig.
Treatments have gone well and I’m very satisfied, although I have found it really does depend on the technician doing them. My usual aesthetician has taken a break for traveling but she recommended who I can have in her absence. Also, their pricing structure used to be very clear, now it’s more complicated but if you can work out what you will probably need and go during off-peak times, you can save a fair bit.
Basically I am satisfied but you do need to be fairly on the ball and speak up so they don’t take advantage of you. I think it’s the same at most places. i.e. my usual aesthetician was very thorough and hardly missed patches, the one time i had someone else, there were lots of missed patches as she drew the boxes too big. If this happens don’t be afraid to complain and/or ask for someone else.