Update. Thanks to those who have replied. It seems the UK is unique in its harshness on this matter ( 2years off post treatment for brain mets regardless of symptoms). My dossier is coming along – the Australian guidelines are far more reasonable, and it is surprising that the USA seems not to withdraw licences unless a seizure occurs.
I have received a helpful letter from my Oncologist / Gamma Knife surgeon, but he has yet to be specific in his opinion as to how long – post Gamma Knife – I will be free of seizure risk. If I can persuade him to give such a specific opinion , it may improve my chance of reducing the tariff to one year. I am loathe to use the Courts as a failure could saddle me with huge costs, even if I have a strong case when I look at International comparisons.