I will repeat my previous suggestion on this matter - when the DC go back to school, find out if they need any extra parent volunteers to travel with the children on the coach/train whatever and offer your services.
Failing that, I would definitely opt for going by train. It will give you a chance to catch up on some reading (whether light or heavy is up to you!)
Now for some arse-kicking: as others have said, you are still, in your mind, allowing him to be a good guy. You are still blaming BB for any of his shit. THIS HAS TO STOP.
It might be at her instigation BUT it is how he chooses to respond to it that determines how much of a knobcheese tosser he actually is - and so far, it's an enormous one. HE IS MAKING THE DECISIONS, not her.
Tell him if he wants to get a ticket to the concert at the O2, it's up to him - give him the contact details to obtain one. Tell him that any arrangements to travel and stay over are his business, not yours. YOU are sorting yourself out, HE can do the same. There need be no further conversation about it between you - he can tell his DD that he will or won't be there, that's his responsibility.
And please - start corresponding by email, not text. And KEEP them all. Good idea to get a new phone - you're getting harassment calls now, so ditch the old one. Switch it off. Lose it. Stamp on it. Drop it down the loo. Any or all of the above - but get a new number.
Keep going - you're doing great - remember for every small slip backwards you will take strides forwards. :)