U2 vs BD - completely different product and with the way Stelios is being lately, doubt it'll happen, I really do. LHR isn't grounds for a budget airline - people only go to LHR for connections, U2 don't want to deal with that.
My personal opinion is:
Regional -> Eastern
Baby -> Jet2 (they have big money people behind them) OR U2
Mainline -> BA/IAG or AF/KLM
That's the only bunch I can see working, honestly. Eastern has been touched upon before, they already operate the Regional aircraft types. Jet2 need spare a/c it seems, most of them have catering trolleys stuck out of the side of them (joke) and U2 have handled mergers before, e.g. Go.
Mainline is tricky, I think Mainline will be the struggle and unless someone like IAG/BA or AF/KLM comes along - I don't think 1) It's going to be affordable for anyone else like Jet2 or 2) It's going to be able to be revived by anyone else.
Good luck to all affected by this drama anywho!