Mart,
Just to say I understand why you did what you did, but as you live in the UK and have employment law's to follow, I hope he dose not try to get you up on wrongful dismissal, I'm not saying you was wrong in doing what you did, if it was me I would have done the same.
The thing is you have to sit down do and investigation in to what he was doing, ask if you could help him in any way, the following disaplinary pros, you would have to then give him a writen or final written for it, any verbal waning will not count, so it had to be writen, then a follow up if you get a writen you can go to dissmisal, or a final you can got to dissmisal, again you have to follow the work act 1974, or you could end up getting fired your self for grosse missconduct or fined if you are the CEO for wrongful dismissal.
I hope the fool dosen't do anything like this as this kind of person need to be fired, but please watch your self as this may come back on you. I am coming to this from what i have read and you may have done every thing right, but I just thought I would let you know