Sex is only a big deal if you've never had it.
A WG won't care what you look like, only that you treat them as a human being, are clean, don't mess them about and pay up, but I wouldn't advise paying anywhere near £1000, especially if you work long hours for low pay.
You will probably cum the second she even looks at you, so I wouldn't advise booking for several hours either. Try 30 mins or even an hour to give you a little bit more time to be relaxed, and save the rest of your pennies to move on and fuck someone else, because once you start fucking you wont want to stop.
As for recommendations, only you know what you do and don't like, but when you find one that you do, do a search to see if there is anything good or bad to say about them. If someone has something bad to say, bear in mind that experiences are subjective, so unless they did something absolutely horrific, don't get too hung up about it.