pain, numbness, tingling - trapped nerve or something else?

On 15th July, while driving, I started to get a horrible sensation down my left side. Numbness, tingling, and pain in my arm, from my neck down to my fingertips, and right down my left leg. I felt ill, and honestly thought I was having a heart attack or something, but kept on going (denial is a stong drug!).
When I saw my GP a day or two later, she said it's a trapped nerve in my neck causing the arm symptoms and sciatica in my back affecting my leg. She gave me some exercises to do for the neck, and I continued to work for the next two weeks but found the symptoms were getting gradually worse. Finally on 6th August I went back to my GP and was signed off work, and have been off ever since.
I've been having physiotherapy twice a week for the neck problem, and doing prescribed exercises daily, but nothing seems to work. Any movement involving my left arm or hand - even walking! - aggravates the symptoms. (No treatment so far for the leg, probably because I've had similar problems for years and just put up with it).
X-rays show some degeneration, but no more than expected for my age (47), although my physiotherapist said that my neck is straighter than it should be, i.e. doesn't have the natural slight curve.
I'm now waiting for a referral to an orthopaedic surgeon, for his/her opinion on what's causing all this and (hopefully) how it can be fixed. But I've been reading a lot of stuff online, and I'm not entirely sure that a bone doctor is the guy to see (no disrespect intended, I'm just a lay person after all).
The pain varies - deep sharp pain in my shoulder, yet similar to dull toothache in my arm - and the numbness and tingling happens in my thumb and my third & fourth fingers somewhat randomly, as if the sensations are moving around.
Does anyone have any idea what's going on? Tweet