Hey there, great to see your enthusiasm! A bit of background on AS English - it’s a real challenge, even for CIE students, and there are a lot of texts to learn, so it’ll be a substantial workload to commit to! Of course if you’re aware of this and you’ve got a school who is willing to help you with this (and plenty of help!) then there’s no reason why you can’t.
Classics is often self studied, but History is in the same category as English in that there’s a lot of content to learn. What I’d recommend is looking at the relevant syllabi on the CIE website and making a judgement call based on how much time you can commit to it. Another option to consider is sitting Scholarship exams - these are also a fantastic challenge