I've also spent (and continue to spend) a LOT of money on post spinal surgery physio. I got 6 sessions on the NHS, and was told that 'well, this is all we can really do, and this is probably the best outcome you'll get....' I get a lot of relief from hands on physio services, so it's worth the £40 a time for me, a couple of times a month.
Interestingly, I had my first spinal surgery in a private hospital, but on the NHS, through a waiting list initiative. I liked my surgeon, I had a private room, better food, Sky TV, and it was adequately staffed with HCAs and nurses (this was the biggest thing I noticed!) I found that I got more rest, and could have visitors whenever I liked, and for however long I liked. I had to go about 60 miles from home for that.
My subsequent spinal surgeries were done in the specialist NHS hospital, also about 60 miles from home. The surgery went well, and staff were attentive. The biggest differences were being in a shared ward, and not getting much rest; the food was TERRIBLE (I had a friend stop by the M&S nearby on almost a daily basis, as you were only allowed 1 veg/1 fruit with each meal!); visiting hours were somewhat awkward, given the travel time for family/friends; and the waiting time for a physio/medication/discharge documentation was interminable.
Unsurprisingly, after three spinal surgeries, and numerous other procedures, I can't get a private healthcare company to insure me..... Even though I now need a hip operation, I'm told I am too young/waiting lists are ridiculous. I'm seriously considering taking some cash out of my mortgage, and just paying for it.