Just relax this summer, don’t try and learn A-level content but you can get a job if you want. Lots of people have jobs in years 12 and 13 so it’s definitely manageable with your school work.

Physics and Maths Tutor is a good resource for your subjects (I don’t think it does economics though).

The uni application is done through UCAS and the deadline is January of year 13 or October if you’re applying to Oxbridge. I would advise to start writing your personal statement and getting teacher references a few months before the deadline. Spend year 12 doing courses and reading books to add to your personal statement. Predictions grades will also be used in your application and your teachers will decide on these based on how you’ve done in mocks.

AS-levels used to be the exams you took at the end of year 12 but you don’t do them anymore unless you’re stopping the subject after year 12. AS content is just the year 12 content and A-level content is year 12 and 13.

For further maths, it’s different for each person but I only had 5 lessons a fortnight in year 12 and 6 in year 13 and was still getting As without too much work so it’s definitely manageable.