All second-hand from people at the airport ( but this is a rumour site )
1. BIA was closest diversion location with United presence
2. Passenger & baggage removed into gleeful hands of PSNI swarm
3. Aircraft fueled for departure but problem encountered securing hold door
4. Given that flight was already running four hours late, crew timed-out whilst trying to resolve door problem
5. Crew decamped to hotel and passengers played find-a-room lottery
6. Crew have exceeded their duty hours for the week and new crew being flown-in from Heathrow
7. Departure anticipated Sunday evening
Some inaccuracies in those statements, the below came from a former fellow worker at BFS who I have known for 10 years and while not directly involved with the flight provided this information.
BFS was the closest (and probably the quietest) after the fuel dumping, crew wanted aircraft on the ground as soon as possible... No PSNI attendance at aircraft, just the BIA Police. No issues with hold door, was all down to having to secure the passenger, statements, cabin checks, paperwork, refueling and getting to the end of the runway, I believe they missed their window by less than 3 minutes. Departed the next day with the exact same crew.
Think what made this even worse was the fact that there was no hotel availability. Was good to see that the airport coped a lot better than last time there was so many people forced to sleep in the airport during the surprise snow a few years ago, have had plenty of delays myself but never experienced something like this thankfully, I am sure these folks are glad to be back at home now