Hi Ragdoll
XXShell is right, each healthcare trust in the uk has a set of criteria for people it will treat, for most it is a BMI of 30 or less, that said in my area that is specific to actual "help" (ivf etc) and not the actual tests. You should be able to google the specifics for your area or ask your doctor for a copy, but as the tests take a considerable time I would be asking for these alongside your journey for a lower BMI
Hope this is of some help, good luck x