Well I did English Lit/Lang, History and Business in one year, AS and A2. Found no real difficulties except for History but that was just the sheer volume of the stuff there was. [Cold War, French Rev, Russian Rev etc] Very doable though.
Go for it and All the Best. Btw if you're going CIE exams, always always ALWAYS check out their marking scheme and work from there. Essays are pretty easy once you've nailed down exactly what they're looking for. Its usually
Knowledge, Application (worth 30-35%) Analysis, Evaluation. (worth 65-70%)