Just because the freeze stopped the pain, doesn't always mean that is where the problem is. Back pain tends to travel down and the freeze may have only deadened the nerve to not feel it. I get that kind of pain and I have osteoarthritis in my lumbar region and my physio told me I had a really tight sacroilliac joint. I have a disk bulge between L3/L4 and one at L4/L5 - these are both felt in my hips and upper thigh. The arthritis betwen L5/S1 cause pain closer to my feet. I'm a US citizen so I can't help you there. I would get a second, third or fourth opinion before considering surgery and wouldn't the MRI have picked up the tear? Maybe you could take your MRI films to another doctor as a first step?
Hope you find answers!