I don't think you're too old at all - I'm 25 and planning to go to uni next year. All universities will have mature students so there will be people your own age and you won't actually be that far off the age of a lot of people coming straight from college anyway!
As for the choices, I think if you want to study English at uni then it might be worth thinking about English Language as well as English Literature? I did Drama as well and loved it, but that was when I was at college so it wouldn't work for distance learning if that's what you're doing. Oh and Psychology is interesting as well.
My advice as someone who has tried a variety of things is that what's most important is doing something that really interests you. You'll enjoy it more, work harder and do better.
Don't let your age put you off uni. Most places like mature students because they have a lot to say, lots of life experience and can contribute in different ways to discussions etc...
Like I said I am Bilingual, I don't think I would learn another language.
Also, would there be any problems if I took three AS subjects in the first year, then in the second year when I'm doing three A2 subjects, take an AS too. Usually people take 4 AS subjects in the first year, but would there be any problems if I did the above?