> tatties for all my life.
Hey, a fellow Scot? ;)
Assuming so, something that might be worth considering is medical cannabis, which has been legal in the UK since 2018 - I mention it, as very few people are aware of this. Both THC oil and dried cannabis flower for vaping are available. I use it for chronic neuropathic and muscular pain, and it works amazingly well.
Alternatively, as some others have mentioned, your body may not process codeine correctly (quite a few people can't), so you may wish to try co-dydramol, a mixture of paracetamol and dihydrocodeine. I personally found dihydrocodeine to work much better than codeine.