It also depends on your age and size bracket. You need to compare apples to apples!
200/hr in London for PSE and under 25 yrs old I think would be fair but you wouldn't be able to charge that in Yorkshire.
I disagree with you on the age and size thing. I'm older than you and I stay busy at a higher rate. Our mutual friend is both older and bigger than you and is busy at a higher rate.
Wherever I am, I look up women in my age bracket and there are always a few who charge below average rates. What they all seem to be have in common is an air of "I'm not worth more."
Few punters will pick Escort B over Escort A if they genuinely fancy A, just because she's ?20 cheaper. Those that do are probably not the sort we want to see. "Well, I wanted to fuck that hot young size 6,but I can't afford her so guess I will shag this old bag, instead."
There are usually a few who charge the same as or more than I do. They generally exude confidence and seem "worth it." If the grooming, the photos and the wording convey something special, the punters will be attracted.