Thank you very much for the comments!

I saw a chiropractor yesterday who found a huge amount of tightness in my traps and neck, and even just working those with a ball has massively improved my shoulder mobility. But I will definitely check out the HawkGrips and your other suggestions (to be honest, I am going to have to google a lot of what you say as it is all new to me).

Thank you so much for taking the time to take a look and make recommendations – I really appreciate your help!