Well, it's over.
The conversation went okay, I had to basically push for it though and for him to say things. He sat in silence until I asked whether he was going to say anything, seeing as he's the one who was doing the thinking.
It was basically a repeat of Monday. He felt as though he had no say in anything, that I was controlling 
, I asked him for examples of this, he couldn't give me any. I said to him that by describing me as controlling, he's making out that I stop him doing what he wants to do, whereas I feel as though I just push to get things done as otherwise they won't get done.
So eventually, it reaches a point and I do need to just come out and ask him, is this it then? And he nods his head and says yeah. I ask him whether he meant it on Monday when he said that he didn't want to get married, and he said he did, so I agree that it couldn't be fixed as what have we based our relationship on. I did say for the record, he proposed to me (and I pointed to the exactly where he did it) and he had two years of planning to tell me this. He said he thought he was just going through the motions.
At one point, he said to me that we will try and just give it a few weeks being separated to see how we get on. I told him no, that I lived this week in hell not knowing for sure what is happening.
He's apologised, said he never meant to hurt me and told me he will always have feelings for me. I'm so calm, I think I am scaring myself. We talked about some of the practical stuff. He's going to stay living here and I'm going to stay too, so I talked through some things we need to think about for making it work as best as we can. I told him that the bills will be split equally, and we need our own space. But I will act civilly towards him and expect the same back.
He actually showed emotion and cried. He asked for a hug. It's over, but it wasn't awful. I did myself proud!