Sorry to reply to my own post but missed something Barbara mentioned..
Useful Medical Tests would be:
Neuro-opthalmologists assessment to look for Swollen Optic Disk (sign of raised intracranial pressure). If found, then a course of Diamox should help, it certainly did for me.
Neuro-otological assessment to look for any other causes
How do you go about getting these referrals? I suspect both are at centres covering the whole country?