How to get a prescription for prednisone?

I have a very painful condition that the (nhs) doctors think might be caused by an auto immune condition.
I'm having to push for tests and it's like wading through mud and each appointment I have to wait 3 weeks at a time.
They've prescribed over 5 different pain killers and NONE of them work.
One of the doctors did say that if it is this certain condition then painkillers won't work but prednisone would bring rapid relief.
But, they're insistent on testing for other things first. Which is taking a long time. In the meantime I am left in constant agony and have been for over 3 months.

I don't see why they can't prescribe me a short course of prednisone just to see if it has any effect, while I'm waiting for these other tests. But it's not happening. I never speak to the same doctor twice as it is and never get a face to face appointment.
So, I am going to try and get some over the Internet, or are there private doctors that would be willing to prescribe me a short course?
I know that prednisone has to be taken with care. All I want is one week's supply, just to see if it works and has an effect on the pain..
Any ideas?
(I wish people, especially doctors, could see pain)