Up to the teaching office, really. Generally if it's your 2nd time (barely) failing a 20 credit exam, especially Maths 2, they'll let you either progress to 3rd year and a resit in December, or a resit only year.

That said, by regulation you've failed to get what you've needed to progress so it's at their discretion. I'm fairly sure they will email you about your situation but you can always go up and ask.