FulhamFC,
Firstly may I extend my heartfelt sympathies for your predicament.
Having lost my Class 1 intially due to 2 "episodes" which were then diagnosed, I am only too familiar with some aspects of the CAA and also the medical profession.
The key issue is not a class 1, it is your personal health and I can attest that health is taken for granted until it all goes wrong.
The neurological system is a fiendishly complicated one and the workings of the brain are something we still understand very little about. For every form of collapse there is either some fault within the brain (can be ailment/illness or a mental reaction as a safeguard due to trauma or stress) or some fault within the supply system be it low blood pressure, hypoxia or even low blood sugar levels. The key issue here is that the correct medical tests need to be carried out because without them the hypothesis can be as traumatic as the ailment.
I use the word ailment because quite simply it is not normal for an otherwise healthy individual to fall unconcious as a result of standing up.
I would refrain from seeking a cause through the internet because you'll find answers from ear infection or low blood pressure through the full spectrum to some really nasty stuff I would not care to mention. None of this will provide the reassurance or answers which you will need as I am quite sure the CAA doesn't use wikipedia for it's medical decision making.
I can however advise the following:
Get a confirmed diagnosis (if at all humanly possible)
This is for two main reasons. Firstly the CAA will not give back a class 1 to anyone who has had 2 or more instances of unconciousness if the cause is not explained. Their satisfaction that you are safe in a cockpit is a risk assessment of the probability of incapacitation. This is where the CAA and some healthcare professionals may differ. If all of the necessary scans are done but inconclusive and you have no further episodes, your GP may be happy that it's nothing serious even though they aren't quite sure what may have gone on. As examples, a transient ischemic attack (more commonly called a mini stroke) is often something where little or no evidence shows on a scan some time after the event whereas transient global amnesia is a known condition which is only diagnosed through direct observation of symptoms or the patients account as it does not show on scans at all! I very strongly suspect CAA will not re-issue a class 1 for something undiagnosed.
The second reason is piece of mind. In my case, medically it all went t1ts up big time, but I am much better equipped to cope through knowing what is going on than through ignorance.
In such circumstances, the internet is not your source of answers nor is it your friend. A lot of information on it is factually inaccurate, and likewise there are over 400 listed causes of unconciousness on one medical website! Granted some are common and some less so but the point is that it can't be second guessed.
This is a difficult time for which I can empathise, however the best thing about pprune is the available support from wellwishers which is quite staggering at times.
Hope all goes well and keep us updated, kind regards,
Ps I am not a doctor, but my experiences have opened my eyes somewhat.