There used to be a girl in London and South East who worked under the name of Princess Lena who did Cosplay. She was quite expensive (£250 an hour) but has a good range of uniform and she seemed to be geniunely into cosplay as a hobby and not just wear those cheap stuff from Ann Summers. She was quite difficult to book and I haven't seen her profile for quite a while though.
If you don't mind trekking over to Reading, there is also Inara Serra who does roleplay and dressed up for the role.
