You don't need really need A-Level Music, or any formal musical education, to pursue a career in music or music production. Like other A-Levels, Music is mostly based around the academic side, i.e. writing about music, which yes, generally means classical music. Depending on your specification and college, you might study some popular/commercial styles, but the approach will be similar as with the classical pieces. For the composition component you can do what ever you want, including music production stuff, but that only comes out at about between 25-30% of the A-Level.
Even if you don't take A-Level Music, you'll definitely have more free time to make your own music whilst in college/6th form (although bear in mind that lots of that time is gonna get eaten into by A-Level Art).
If you do take A-Level Music and go on to study it at uni, Music courses are pretty flexible. Of course you'll have to do lots of stuff with classical art music, but there are usually opportunities to take modules in music technology and production (I think it was Surrey in particular which I remember had lots of music tech equipment and studio space, but most unis do to some extent). On the other hand, vocational courses in music production, which might be a better use of your time if you're solely interested in music production, don't require A-Level Music anyway.