Thanks everyone for your support  

Thank you @Mix56 and @QuentinBunbury for the prep tips! Financially it's fine, we've already said we'd split everything 50/50, he's said he won't pay maintenance but we can deal with that further down the line.
In terms of immediate childcare arrangements, there's no way he'll move out, and I'm the primary caregiver so I won't either. So I think he'll want to have some sort of birdnesting arrangement with 50/50 presence until we sell our house, which I'm not happy with as she is very attached to me as her main carer and I'd much rather a very gradual approach. But we'll have to see where we get to.
Your nerves will be screaming at you that you're doing it all wrong, because he will be upset, and you'll want to minimise his upset, and you can't, unfortunately.
This is what's happening even anticipating any sort of conversation!! If he is near me and things feel tense I immediately need to try and dissolve the tension rather than allow it to be 
I just cannot picture being able to actually speak up and spit it out.
Once he gets half a sniff of the sense that he's losing control of you, you might find this miraculous change reverses somewhat. Consider how you might maintain your internal resolve when that happens, as I suspect is probably inevitable.
Yes, and that is my concern, that I'm going to spin this out for ages and continue to torture him in the meantime because I am so desperate to make things ok whenever he's angry or sad. I have zero internal resolve. You're right though, he is likely to call it before me if I don't manage to sufficiently act like I'm ok. I'm just feeling very very sad for him whenever I look at him and I think he's picking up on that.
@FoxgloveSummers in terms of me being flaky with my friends, they've all stuck around luckily, they're a lovely lot 
my husband wasn't trying to stop me from socialising or seeing people for any sinister reason, his main concern or irritation would have simply been things inconveniencing him or not fitting in with what he'd planned for himself. Just part of his extreme dickhead persuasions I suppose!
@wrigglewriggles thank you, yes you're right that he's not really been thinking of me properly. But he has been trying very much to process my affair, attempt to forgive me, and still desperately wants us to be happy together. I've asked a lot of him these last few months in terms of things that have stretched him emotionally and I suppose I didn't have much bargaining power after cheating, but he's tried his best to make things work. And I'm not trying to defend him here, just feel very sad for him, as I may have mentioned once or twice 
Just don't know how I'm going to be able to do this to him!