It is very frustrating Tabbycat
If you've got a follow up in Sept your Neuro should be arranging all your scan appointments for you, I had a mri and then i think it was 3 months later was the dat-scan with nerve conduction tests inbetween, i waited a further 7 weeks to be told the results. the Gp and Neuro both knew those results, i was at the end of the line of importance in that the Neuro thought the Gp would be the one telling me the diagnosis which didn't happen. they both knew within a week of the dat-scan.
all you can do i spose is chase and chase the neuro/pd nurse or secretarys too get them both date confirmed.