Plus ones!

Ok ladies let's talk about plus ones! We have decided that we aren't doing plus ones because that could easily double the guest list and the budget. We are however allowing people who have been in long standing relationships to bring their SO. Now the issue is that my fiance's uncle's friend decided to invite himself saying that we couldn't get married without "Uncle Ernie" he is in no way related and up until this past week I have not met him. He is not close to my fiance either. When I tried saying that the guest list was set along with the seating arrangements for the reception, my fiance's uncle said well he's coming as my plus one. Both men were completely drunk at this point, there was no talking to them. Honestly my fiance's uncle is lucky that he's even on the guest list (one of those you have to invite so that so and so doesn't get mad kinda guests), he is constantly rude to me and our kids, he lies about us to my fiance and my fiance's family saying how we hate him and are always so rude to him and so on and so forth (if it wasn't for this behavior I would have no issue with the man). I told my fiance that he will need to handle the situation as if I do it it won't be pretty (trying not to turn into a bridezilla, and trying not to let the wedding stress me out too much), but I know that if he does anything at all then it will most likely be that they talk him in to it because that's just how they are and my fiance doesn't like arguing with them or putting his foot down when it comes to them. If the wedding day comes and he shows up uninvited what should I do? I do not want this man there at all he does not have any kind of relationship with either me or my fiance and we're wanting only people that mean something to us to be there.