Rectifying the APU fault, getting the paperwork done and getting a new departure slot created a 90 minute delay to push back. The captain has been great at keeping us informed, and crew handing out cold water.
I know it's unavoidable that aircraft go tech. It seems to be happening more on BM at the moment than I've experienced previously or on other airlines, creating delays to flights. (The mid-morning BRS-BRU is likely to be delayed as a result of this too).