Congratulations Hannah a) on surviving b) on clearly having such an interesting thesis that they could talk so long about it and c) on the good result! First, wait until you get the formal report - that should list exactly what changes need to be made. If you've got 3 months they will despite being labelled major be relatively limited. When you get the report, agree with your supervisor what you are going to do on each point and be incredibly systematic. Make a timetable, keep track of exactly where in the thesis you have addressed each point and just work through them. In some ways as they're broken down into chunks of work, it's easier to combine with a p/t job than writing a chapter from scratch. You can do this - one last push and you're there.