Oldbird: I chuck this in 'for what it's worth', which might not be much...
I had/have tinnitus. A wise old ear consultant about twenty years ago advised me to get my sinuses cleared out following an MRI which showed bunged-up sinus tubes.
I did, and my tinnitus went from v.bad to not bad. I still get it, a bit, but it's always better when I've used Flixonase or similar (heavy-duty nose spray) to keep them clear. Apparently, if the air pressure on the NOSE side of the eardrum area is not right, it can adversely affect the drum and in SOME cases worsen tinnitus.
Might not be the case in your ears, but worth kicking about with your ENT consultant, if you have one.
Good luck.
ALlen.