You do not want to get into the whole rent by the hour bit, it just creates bad feeling in the long run, especially if the owner disides to rent the space to another tech when you are not there. Which she is quiet likely to do. She wants the rent, she wants her hair clients to get their nails done when it's convienent to them and most of them don't care who does it so long as the client is happy.
Things to take into account:
Where is the table? Right by the window is best for you, plenty of natural light, you are highly visible and it gives your clients something to stare at, which means they are more likely to keep their hands still!
Will they advertise for you?
Will they take bookings for you?
Do you have a locked cupboard for your products?
Can you use their debit card machine to take payments?
As for how much to pay that very much depends on where you are and how much competition you have around you. City center, only tech there? Expect to pay more, loads of techs around you? Argue to pay less or less to begin with while you build up your client base.
Village, only tech? Then do your research and see if you have/ are likely to have a client base.
The avarage seems to be about £70 a week but I've seen much higher for prime spots in London and Birminham