when did you start revising in year 12?

Exams were at the beginning of May so I started 2-3 hours a day in the middle of April. - I suggest you start earlier if you are going to AS in September.

I am planning to stay on top of my work from September and do like 1 hour a day and increase it during mocks.
I learnt my lesson from GCSEs to leave things last minute

Is it true that how much you learn in year 12 is equivalent to how much you learnt in year 10 and year 11 combined? If so then that is a LOT of content.

''I am planning to stay on top of my work from September and do like 1 hour a day and increase it during mocks.''
That is really good, cause I planned to read through what I learned that day after school and practice a few questions. But that never happened, I was too lazy lol

''Is it true that how much you learn in year 12 is equivalent to how much you learnt in year 10 and year 11 combined?''
What you learn in yr 12 is equivalent to yr 10 and yr 11 combined maybe more. There will be more content to cover - I had 22ish books in total (yr 10+11) for chem GCSE and after I finished AS chem I had 16 books in total - 8 books per exam(and another 16 in A2). As you see the number of booklets got shorter. But the content is that hard part there is just so much to cover, when I look back at GCSE's we barely covered anything, in A level I learned A LOT more things.
Just try to make sure you understand everything from the beginning and do a lot of past papers in exam period.

Can I ask what you chose? Maybe I can tell you any resources I used.

I didnt

Did you regret it?
Did the workload become overwhelming during exam periods?

Thnx for the advice. Really appreciated
I want to take chemistry, biology and maths

btw - Should I study during the summer especially for subjects like maths so I don't forget it?
I think I have entrance exams for them in September. not sure tho

If there is no exam then you don't need to revise anything. For things like maths, they will most probably go through some GCSE topics then extend on that knowledge for A level content. Although, if you are really bored in the holidays you can. No harm in being ahead for a couple of lessons

''I think I have entrance exams''
I didn't know there were entrance exams for sixth forms/colleges
Well in that case, yes, revise lol
Did they tell you what the entrance exams are on or topics to learn? But why do they have entrance exams if you already get your GCSE grades before 0.o

I think the best resource is just to buy the exam board revision guides. Or you could check your local library if they have any.

For maths, honestly, the best way is just to keep practicing questions over and over again.
But this TSR thread has some pretty good stuff - https://www.thestudentroom.co.uk/showthread.php?t=5860630

For chem I used https://www.chemguide.co.uk/
If you go on YouTube, search 'Eliot Rintoul' that guy has some pretty good explanations.

I am not sure about biology though sorry - didn't take it :/
But a website called physics and maths tutor has a lot of past paper questions and revision guides for sciences and maths.