Wake up lady!!!, what does he need space for?
If you were having problems before his ex girlfriend's announcement, don't you think, his space issue's are just an excuse, obviously, he isn't mature enough to be honest with you, and deal with his NOW ISSUE'S with your relationship, I don't think his behaviour has anything to do with his ex, her relationship, certainly has nothing to do with him, she has obviously moved on, and as you say, with her boyfriend for some year's.
Sound's to me like your boyfriend has been allowed by you, to make you feel bad enough , to write your concerns on here.
Sorry if I am blunt, but he needs to explain to you, what his issue's are, I think it's about your relationship, and he is using his ex as an excuse, to do his own thing, and speaking plain and simple, if you do not nip this running off for some space, now, you are enabling him to do it in your future relationship, because , he think's its ok, you have let him create this situation, rather than say look, I'm not prepared to put up with this behaviour, sit and talk , like an adult, not run off on a hotel jolly, how old is he 10.
There is more to this believe me, I have lived this, Beware, he will run every time.
Best of luck, and I genuinely mean that, this situation if it continue's can totally mess with YOUR HEAD, if you let it, you have done nothing wrong, to be treated like this.