I saw Sensual Isabelle a few years ago and she does CIM. I have not been back since as I remember the place she operated from was difficult to park my car (fairly central Chelmsford) and her place stunk of fags. She was also slightly larger than I thought at the time, but I think others have said she has toned up more recently. Really nice GFE though.
As for Chelmsford itself, I can't really remember any girls who I would see for a second time in the area. IMO it's either fairly expensive or a lot of touring girls. Chelmsford is fairly easy for me to travel to so if anyone can shed any light on decent girls I'd be interested.