Missed offer with Big 4 firm

Hi Everyone, I need some advice that doesn't involve a time machine.

I am in a terrible situation right now. I just received my exam results and I received a 2:2 degree... (2.9-3.0 GPA for the non-British). While this is already bad considering virtually all jobs require a 2:1 degree (3.3+), it is even more frustrating as I have a job offer already on the line (Big 4 CF), so my professional career is in jeopardy.

I have emailed everyone I know at my university who may be sympathetic such as my academic supervisor, the administrative staff (I received a nice personal thank you email from them), etc. Extenuating circumstances may be available, like COVID but I am unsure if they will budge, as I was never infected during exam season.

If the worst come back and there wasn't any glitch or clerical mistake with the marking, then what do I do? In your experience monkeys, do Big 4 firms instantly renege on you if you don't meet their GPA/degree requirements, or do they have a laisse-faire attitude and still let you join? (I don't mind staying with them forever)

Worth noting, that I got this offer from converting over the summer and a previous spring week so the team is well aware of me and fully expect me to join.

All thoughts and ideas appreciated. :)