In my NHS trust you need to have the symptoms for 3 months before they refer you.
I had this on and off for 12 years, it was only when the disk 'went' and I was in pain for 3 months straight that I was referred to the spinal unit. The Dr laid me on my front and started to press on the disks in my spine, when he got to the problem one, he barely touched it and my reflex made me kick him in the face
.
He told me to stop physiotherapy, and be really careful about what I do. At this point I had been put on gabapentin which has been a godsend. I had my scan, and the technician didn't tell me the results but she also told me to be extremely careful.
I'm now waiting for a nerve block to see if that helps.
That was very long winded but what I'm trying to say is hang in there, and keep going back to your gp.
Between the gabapentin, antidepressants, tramadol, ibuprofen and sometimes paracetamol, I take about 30 tablets a day. I'm surprised I don't rattle.
There's a fantastic thread on the health board and it's full of people who can give you advice and support, a hand hold and somewhere to vent.
Sciatica is awful, and I hope you find some relief soon. 
(Dear lord that was a fucking essay).