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i recommend starting here:

http://www.adassoc.org.uk/html/careers.html

as for which A levels to take, it doesn't actually matter a whole lot in determining whether you get onto a uni course.

i imagine the media studies would serve you well, but it really isn't neccessary.university courses will snap up students no matter which A levels they took. it's all about ucas points nowadays. so long as you meet the grade entry requirements, it usually won't matter what you got A levels in.

it might be worth checking out a few of the uni course websites on their entry requirements, but i doubt they'll specify which subjects you need to get A levels in, just that you get high enough grades.