Look at the rota to see who's on and see if she has any reviews would be your best option and like badsin says I would go for the full service rather than just a massage and happy ending. There are plenty of places in the east Midlands who will offer better value for money if it's just a massage and happy ending you're after. I have not seen many here but Tori I would recommend
Good advice all round, Mr B. I'd certainly endorse your suggestion of Tori; I have to declare, Nigel, that she's still my favourite

so I daresay I view her through rose tinted glasses, but I'd be very surprised if you were disappointed with her. She's never given me a massage, but she takes great pride in her work, and I'll bet a pound to a penny that she's very, very proficient.
One final thought; if it's a particular service you're after, it wouldn't be a bad idea to ask the receptionists. They're helpful, efficient and they've seen it all before. They'll know which girls are the best masseuses, and they'd make sure you were given a room with a proper massage table in it; they might all have, come to think of it, but I'm not sure.
I hope you enjoy the occasion, and there'll be plenty of us looking forward to your report!