I suffered with a shoulder problem for a good few years. My local GP was giving me a steroid injection on an annual basis which mproved things for awhile but the problem kept returning, hence another injection.
On relocating to Yorkshire I saw a different GP who refused to do this, instead he referred me to a specialist. This bloke did a series of 3 steroid injections 2 weeks apart. The way he did it was really painful but I've had no problems now for about 12 years. This may not be suitable for you, Tony but I would at least ask your GP for his thoughts on that approach. If you do, the specialist I saw did mention his opinion GPs can't do this properly, he did do the injections differently to the GP and though it hurt a lot, it worked and was worth it.