Hello,
Well done for getting through this far. From what I remember, OASC was the hardest part!!
With regards to your migrane situation, I think (im sure I will be corrected if im wrong) that GP's can put notes onto your medical records to the effect of "...suspected but later proved not to suffer..."
I remember years ago when I was a kid, they thought I may have asthma. I did all the tests etc, clear cut asthma I was told, come back for your inhaler on...
It turned out I had a mild chest infection, hence the wheezing, shortness of breath etc.
This was worrying me so I simply got an appointment with my GP and voiced my concern. He looked at my records and told me that there was no record of asthma so I was clear.
With regards to your letter from the neurologist. The RAF may or may not take this into account. From what I've seen of cases where specialist advice is needed, the RAF tend to send you to one of their hospitals and get checked out. Only then will they 'believe' you.
And, like OPSO says, if it goes pear shaped and you know you are right; if you want it that much you will fight for it!
Hope this helps