Self study A level HistoryWatch
They may not let you enrol with only 2 taught A levels.
If you want to take A level History then you will need to complete NEA ('coursework') which would require you to have someone supervising, authenticating and marking your work - for this you would need to enrol on a distance learning course or persuade your school to do this.
You need to pay for the exams by February of the year when you are taking them - sort the rest out before worrying about this.
Take it from someone who mostly self studies due to illness - It’s not impossible, but it’s tricky, and an unnecessary strain on yourself if you could go into lessons.
My advice would be either to self study Media, and enroll in history classes - Or chose between the two. Media A-Level, as far as I’m aware, isn’t a requirement for any university course, so it won’t hinder your future career having not taken it for A-Level.