Hi, I live in the south as well, about an hour from London. I had my endometriosis treated by Mr Trew, the private consultations are done at 92 Harley street and the operation on the private wing at the hammersmith hospital. I've had a quick look at their price list and they quote £2,900-£3,400 for a laparoscopy. I think the first step would be to see mr Trew for an initial consultation, which is £225, when he treated me he did my lap and confirmed the diagnosis and also treated the endo all in the same operation, I agree with you that it seems madness and complete waste of Nhs resources to do the same operation twice, once to diagnose and once to treat.
I would highly recommend mr Trew, he is a fantastic doctor, and was recently voted one of the top fertility doctors in the Uk by the times newspaper. I fell pregnant with my son 3 weeks after my operation with him.