I think sometimes they are trying to see if they can send you to the nurse practitioner instead.
I needed a second set of antibiotics in the New Year when my first lot didn't work. I'd been up all night coughing and rang up on Tuesday 4th January or whatever the first "real" day of the year was (after the bank holiday). I rang as soon as lines opened and was 44th in the queue! Finally got through and of course all the GP appointments had gone.
I cried into the phone (not even strategic, I was that fucked off with the cough and had had no sleep for days) and she aksed if she could put me on the Nurse Practitioners "cancellation" list. I said, yes please. She called me during the school run and gave me an appointment.
So I went in and she listened to my chest and was able to prescribe me some very strong antibiotics and a ventolin inhaler. No sign of a doctor, she obviously has those prescribing rights.
So I walked out of there with my script - who needs GP's eh?!
I think the Nurse Practitioners with prescribing rights are fairly underutilised, everyone just wants to see a GP but there's not a lot they can't do.
I did see one for my blood pressure after having my most recent baby (pre-eclampsia hangs about sometimes a few weeks after the birth) and she was unable to prescribe me blood pressure meds under the circumstances so there is some stuff they can't do. But she got me in with a doc by barging into his office so they have power that receptionists dont have!
It does come across as kind of rude though. Just say "I have a medical condition". "What sort of medical condition" "The kind a doctor needs to diagnose". etc 