I feel for you Tony,
Both of my rotator cuffs (supraspinatus muscles) were damaged during my throat surgery (somehow and I'm not sure I want to know how!) and it has taken quite some time to achieve movement again.
As you may know, early treatment as possible is important, don't repeat the damage, I know that sounds daft but the tear can be due to repetitive micro-trauma and do follow the physiotherapists instructions. Seeing a physio may be useful in getting some help prior to the MRI's. Anti-inflammatories such as Ibuforen may help ease the pain.
I couldn't raise my arms to shoulder height but now I have about 90% movement and little pain so it does come good with care.
I know this also sounds daft, but when my physio gave me my schedule I worked really hard at it and it helped. She was a little surprised how we'll I recovered and made the comment that it was because I followed the program and most patients don't because it is painful and they give up.