Its illegal to pay donors for their eggs in the UK, so I am not sure what your local hospital is up to! But as it says above, you can claim expenses that are capped at £750 by the HFEA. I would speak to Alison at www.altrui.co.uk for more information, she is really lovely!! Altrui is a company set up to match donors with recipients and she will talk you through all of the ins and outs.
The HFEA set a limit of how much egg donors can be paid and it is supposed to cover expenses, so really private units shouldn't pay you more. There is a fixed sum of £750 set by HFEA. It doesn't stop you enquiring! but you are not going to make your fortune by selling your eggs in the UK, sorry.