Oh my I feel the same, I'm in year 12 so thankfully no mocks, but my teachers are setting classwork for a one hour lesson that takes me over 2 hours to finish, plus all the homework that's becoming harder and harder. And I have the same kind of parents - revision all day.
But I am slowly adapting so here are my tips:
Don't do the classwork. I'm assuming your teachers don't mark classwork anymore? Take notes on what's important and do get some practice but don't do all the questions they set. At the very most spend 90 minutes for each lesson - the maximum. There's no point doing a ton of questions just because the teacher set it you - you know how much practice is enough, you know when you've got the hang of it.
'Do' as your parents say. I've had countless arguements with mine and it turned out all to be in vain. What do I do? Sit at my computer and do what I want. Hopefully they don't stare at you as you sit in your room otherwise this won't work. But that's what I'm doing and it's going well for me. Obviously sitting at a screen all day is unhealthy so if I'm actually doing revision and I don't need my computer I'll turn it off and I do try to kill as much time away from the computer as possible.
Organise your revision. You don't want to revise all day but you do need to do enough. I use a list of unfinished homework and revision tasks to keep myself organised so I know what I need to do.
Make the most of your weekly going outside. I haven't been out of the house at all for weeks and my garden has been keeping me alive. Even if you can't go outside walking around the house and looking at the window has become surprisingly pleasant.
Communicate with others. I've been on my phone a lot lately, I've been talking to my friends a lot because I've been feeling really lonely. My parents are actually getting annoyed because I'm on my phone that much. I haven't told anyone the full extent of my situation and I'm not planning to, but simply having friends to talk to has kept my sanity intact.
Do something productive. I never really played games and I've always had quite a boring life. Now sometimes I'm sitting at the computer, unwilling to revise, and I don't know what to do. So I've finally been productive, I've gone and researched universities and careers and learnt new things.
That's it really, hope you find this useful!