usually intial tests would be a sperm analysis for him and hormone checks for you, CD2 and CD21 but if I remember correctly your GP has already done some of these.
depending on what the clinic is like and where in your cycle you are they may also want to do a scan on you to check your ovaries.
are they referring you to the womans hospital or are they expecting you to see them privately?
you can try looking at the hospital website for their fertility section if they have one and that may give you some more idea as to what to expect.
Don't worry, the tests aren't horrible and if they do find something at least that gives you the option of a solution.
Goodluck xxx