I had suggested in my email that he stay abroad till after the Christmas period to avoid awkwardness but of course if he is in the U.K. we can work something out
What was intended to be a cold as ice hard hitting summation of your intentions has included at least one concession too many and if you don't put your proposed response on ice, at least for the weekend, you'll be sucked into corresponding with him and he will see this as sign of weakness on your part.
It's neither incumbent on, or desirable for, you to offer any explanation as to why you don't want him in your home, nor should you be offering any pointers as to how you expect him to behave.
He's also saying that he's not responding to the accusation of adultery and he will defend it in the future
Meh. I didn't expect anything other than denial from him. As for defending the accusation of adultery "in the future", when he consults a solicitor he will be asked if he has committed adultery and he will be appraised of the eye-watering cost of defending a divorce.
If he admits to committing to adultery, no solicitor will advise him to defend. If he denies committing adultery he'll be bang to rights when his solicitor sees the emails he's sent to his mistress but, as I understand it, you'll be filing for unreasonable behaviour citing, among other things, his activities with other women therefore defending become a moot point.
As you've lit the blue touch paper, you're best advised to stand back and watch him tie himself in knots the fall out before firing off any more.
This man is used to calling the shots and he now needs to know that you've got more balls a bigger gun than he has.