AS - It is not often I disagree with you but this time I do.
He does not live here. He moved out over a year ago. This is not his home.
1. He chose to move and call somewhere else his home. 2. He does not contribute to the mortgage and never has (note: I am not bitter about this - if/when it comes to splitting the assets then we will split them 50/50.).
I have asked him repeatedly to let me know when he is coming to walk our dog or when he will have the children here. He says he will then he doesn't. Sometimes he is here all day (the camera is good for something) on his own for no good reason. When I mention it he says something dismissive like "Yeah, I came around to walk [the dog] or "I was waiting for a package to be delivered". If I push him on it, he then says "I can come here whenever I like".
This time he was trying to push me into agreeing to go cheap with the decking because it suited him. He does not want to spend more than the money we put away a long time ago. When he told me his brother was willing to do it cheaply and quickly, I initially said "Thanks. I'll think about it" and went to walk back inside. He called me out again and tried to convince me again and I said "I am not sure that I want to go cheap. I still want it to look nice". We went around in this loop for about 5 minutes, him coming up with reasons we should do it and me saying "I'll think about it". Finally he said "The money is in my account and I say we're going ahead with it". That's when I reminded him that this is not his home.
What was I trying to accomplish ... I was trying to set a clear boundary regarding his status in relation to the house. It has always bothered me. In the past I've done this via wishy washy "can you let me know when you're coming around" or through actions - I treat him like a guest when he's here by saying things like "help yourself to a cup of tea" or "just show yourself out when you're done". I've been doing this pretty much since he left. It has not worked. I wanted to remind him that he cannot have his cake (his flat) and eat it too (treat this house like it is still his home).
We talk a lot on this site about regaining our self respect and putting aside our inner mister nice guy and stating clearly that we will not be disrespected. My H coming and going as he pleases is disrespectful to me.
BTW - you were the one that said the camera thing was, to use your words, creepy AF. Yes, it (was) creepy. But more to the point, it was controlling.