You are not having a good time of it lately are you?
Basically there is no offence in filming you in private as the video source came from either a nother private place or a public sphere. If he was encroaching physically on your property then ther is a civil tresspass, which is not a criminal act, but a civil offence (that is the Police are helpless.
However, if you were doing a private act (uusally sexual or toilet acts in private) highly unlikely at a party, then he could be a voyeur which is a criminal offence. He must get sexual gratification from the filming though and as said normal actiities albeit in private will quash the offence.
If his behaviour is harassing, then it can be deemed harassment under The Protection from Harassment Act, but as his findings have been handed to some authority a simple defence will and can be used.
Furher, as in a private place there is not even public order offences re derogatory remarks.
The law is an ass.
My advice, film him back. Havea polaroid ready and when you see him filming photograph his actions with a great big flash. Your defence to causing him harassment, obtaining evidence for your own harassment.