To all the posters saying 'just talk to him. . . .blah blah' have you not picked up that he doesn't want to talk to her??
He asked for space (in my opinion if that's what you need then you are the one to leave) she gave it to him.
If she'd stayed and tried to force a conversation it would have completely fit into his personal narrative that OP is a bully; and 'forces' him in to things and would have been used as a stick to beat her with: I just asked for a few days to sort my head she couldn't even do that. . . . this is what I've had to put up with'
Now personally I would have said 'I'm not keeping you here; you're an adult, if you're not happy in a relationship with me there's the door. If you want us to continue sharing the flat/house be aware that it will be on a roommates basis. I will not be cooking cleaning etc for you.'
I will also say I'm in my late 40's; I have only once seen a man leave in this manner where there wasn't another wo/man. I've seen couple's split amicably and like something off Eastenders; but this quite sudden change and the rewriting of history; the forced into marriage crap, etc , normally turns out to be the story s/he has told the other person and themselves to justify what a horrible thing they've done.
You're going to find the next few weeks very hard if you move back in and he stays. You need to start telling people so you have a support network in real life or if that's to real see if your job has an type of employee support. You might be able to access some counselling through them; just as a safe place to vent.