@alex_bolland, NICE approved Ocrevus for primary progressive last year. There is a 3 point criteria you need to meet so your neurologist needs your scan result to make the decision for you.
I agree entirely with you though, how you feel clinically is more significant to you than any scan result, I hope your neurologist will take that on board. Scans are only one part of the picture. Fortunately my neurologist is very active about giving treatment.