I do think that, if you are down for elective surgery, it is the word "elective" that matters as far as cancellations are concerned. You may be in great pain, but you are not, essentially, I'll.
If you have read any of my posts, you will know that I have had a few operations in the past year, and certainly the recent hip operation (6 weeks ago) was cancelled several times over the Christmas period. Yes, I was sad, yes, I was disappointed, and yes, I was in a lot of pain, but nevertheless, I can and could see that the orthopaedic wards might be overtaken by emergencies where people were in a much worse state than I was. And there was noro virus too. The NHS is underfunded, and overworked, and on the whole does its very best.
If you are in extremis, usually you are well catered for. Been there too.
My last operation was eventually brought forward. As I had expected, the whole experience was positive and successful.
We need to campaign to get our NHS the funding and the respect is so richly deserves; yes, complain, but complain to those who are supposed to sort things out. Good luck....