Hey Ho,
Just found the answer to my question! I finally realised that because I am flying on a NPPL medical that my controlling medical standards are DVLA Driving Standards, so I Downloaded from the DVLA website : For Medical Practitioners at a Glance Guide to Current Medical Standards.
There is no mention in there of Vertigo being a reportable condition other than as with many other general not specified conditions if it became a relevant disability to effect the safety of your driving.
Therefore providing it does not become a disability it is not reportable. In my case if I suffer a further incident it will be the end of my flying or good sense at least says so, unless of course I restricted my flying activities to the presence of a safety Pilot. In the case of driving it would probably need to be a more regular or a diagnosed condition to meet the disability criteria.
We will have to see what the next two months brings, hopefully no further medical events!