Update:
I got a callback at 9am, which had no noise and immediatley cut off!
I was horrified that my chance to upgrade might have been jeaprodised, but after calling the general line they re-listed me for an urgent callback and assured me someone would be in touch later today.
I got that callback today around 2pm to confirm my details, and they’ve said I should be clear to pick up my passport on Tuesday (24 hours to flight) from Liverpool unless they find any glaring holes in my paperwork!
thank you all so much for your help, and I’ll update again if any problems pop up on monday in case anyone else has similar problems in the future!