Solost - no harm in letting him think that other people are interested in you - after all, he apparently isn't any more but that's HIS fault, not yours - so reinforcing that you are still an interesting, attractive, desirable woman is all to the good.
But - try and avoid direct lies - you'll get caught out at some point. WWIFN is right - enigmatic is the way to be. If he asks re. texts/flowers/drinks etc., just say "no one you'd know". Because even if you have bought them yourself, it's still true - he DOESN'T know the 'you' that you now are.
BB is really living up to her nickname, isn't she?! Dictating how little he can be in your company - what a joke! If she's out of the country, how the FUCK does she think she's going to police it? She'll just have to take it on trust - oh wait, he's not exactly trustworthy, is he. Ah well, too bad. That's what you get for going for someone who is already married.
In the end, it's up to him how he deals with it, it's SO not your problem - but he really ought to man up and just tell the dozy bitch that he is travelling with HIS DAUGHTER and will be staying with HIS DAUGHTER and eating with HIS DAUGHTER - and if you, her mother, happen to be there as well then that's just too fucking bad. BB needs to grow the fuck up. (I'm not sure if you're travelling with your DD or not, btw, she's probably travelling with the school, hey, but BB doesn't need to know that. If you're concerned about getting yourself to London, perhaps the school need more volunteers to go on the coach with them?)
As for "crying" over the Boxing Day scenario - well, what a load of crocodile tears, if they ever even happened. And tbh, why the fuck should you care if she cried? Why on earth is he trying to elicit your sympathy for the woman who helped him destroy your family life? Is he completely fucking insane?
Sorry for all the swearing there - this woman is seriously getting on my tits now.