Firstly, they're really good mock grades, if you got those grades in the real thing you should be really proud of yourself.
Secondly, 67 days is plenty of time to revise so please don't stress about it. I did my gcses last year and I started revising in april/ easter holidays (which was late I know but I'm an awful procrastinator) and I got one 9, two 8s, two 7s, and five 6s. Not my best results but they got me onto my alevel courses and that's all that matters. Don't feel like you should've started revising ages ago and you've got no time because you have loads of time!!
Ok here's what I recommend for your revision:
Science: Do a past paper with real time constraints and mark it to find out your weak areas. Then watch youtube videos on each weak area and make notes (revision cards, mind maps ect... whatever works for you) (I'd recommend science shorts on youtube- they have really easy to understand videos on every topic in science. They have in depth videos on specific areas of topics and more general videos on whole topics and papers) You should also revise all the practicals. For this I'd recommend watching freesciencelessons. His videos are really good because he explains the instructions and analysis very well. Other than that I'd just say more past paper questions
Maths: maths is my strongest subject so I actually didn't do a lot of revision for it 😭 I'd say just do past papers. maths is one of those subjects that to revise it you just have to do it. Again I'd say watch videos for areas you don't understand or ask a friend or teacher to explain it to you. For papers 2 and 3 I'd recommend using predicted papers rather than past papers (especially for paper 3)
English Language: Work on your question 5s because they're the most marks. Make lots of storyboards and plans of what to write. Make sure you know how to answer the other questions though. (I'd recommend Mr Everything English and Mr Salles Teaches English on youtube- they're really good)
English Lit: This was my weakest subject. I liked to make mind maps filled with analysis and quotes and link them to eachother by different characters, themes ect... then I'd use a whiteboard and the blurting method to memorise it. My strongest section was poetry. My school did love and relationships and all the poems were about either family or romantic relationships. I memorised one family and one romance poem and learnt how to link them to every other poem. Whenever I was stuck I just talked about the punctuation (I did this in english language too) because it represents so much (like i could talk about how hyphens represent distance for days)
History: My teachers put on after school revision sessions for this and they helped so much. I just memorised the stories and did mind maps, flashcards and blurting.
Further maths: This is not a priority. Don't bother. I only revised this when it was my last exam and I just did a predicted paper. In my school they just took the people who were good at maths and put them all in the further maths exam without actually teaching us any of it and just told us to try our best. I was expecting to get a 2 max but I got a 6. So don't worry about it because your basic maths knowledge is enough. (although if you really want to revise for it learn differentiation cuz its easy)
That's all I can help you with because I didn't do your other subjects

Final note would just be don't stress because gcses really don't matter. Like I know schools like to frame it like you're gonna end up homeless if you don't pass maths but in reality no one cares. Like just as long as you pass english lang and maths so you don't have to retake them (even if you do have to resit it's not that big of a deal) and you get the grades you need to do you alevels/ btech/ apprenticeship/ whatever you're all good. So don't stress and just enjoy year 11!

Good luck!!
