I think it took the clinic two months to get and process my referral after it was sent, and then - after I rang them three months from the point it was initially sent - I was told that a letter should have been sent to be and my GP, but they don't know what happened to the letter . . . reassured me I was on the system, but that it's be twenty-four months plus before I was given an appointment.

Basically, you can ring whenever for a response, but I wouldn't worry about a lack of a response as they're notoriously slow. If the GIC you were referred to was London, I'd definitely start making calls and be referred elsewhere, though, as they're no longer taking on new patients.