Thanks again for your reply.

If you believe that it might be nerve compression in C6-C7, how would I get that diagnosed, I mean how would someone know that was the problem for sure?

Also, I've never experienced any real discomfort around my neck vertebrae throughout this entire period (although coincidentally in the last few days the bones at the base of my neck have been sore, which I guess would be the C6-C7 area). Would I have not felt some discomfort directly around the area if there was compression, or is it just that that particular irritated nerve root carries the signals from the area that I feel pain (as you can tell my knowledge is poor).

As you say, it is dangerous to make a diagnosis without full assessment, not that I don't want you to make suggestions, you have been brilliantly helpful, it's just I'm the type of person to get fixated and worried about this type of thing.

Would you say this is a pretty standard thing that any physio would check, or would you envisage there to be a risk of making an error such as trying to address the problem as purely about muscular imbalance through a combination of strength exercises and stretching??

It's just I'm not really sure how to go forward with this problem - when I search google for "specialist shoulder physio" or similar, you just get swarmed by websites for physiotherapy practices, that I'm sure are very reputable, but I don't know who really holds the expertise to help me (if that makes sense). Ideally I'd like to be able to go to the doctor and say "I would really like a full assessment to see what the is going on e.g. x-ray, Wikipedia reference-linkMRI if necessary", but they just don't take me seriously now because to them it looks like I've "tried physio, it hasn't worked, so let's not waste any more time, let's look at learning to deal with the pain long term", but instinctively I feel like this can be resolved, or at least improved substantially!