How much is it to take 2 A Level courses as an 19 year old in England?

As you're already 19, you cannot go to a normal state-funded secondary school, so you'll need to explore various adult education options in your area. Service providers vary in their pricing, you'll need to check with each one individually. If you're not sure who is offering such courses, check with your local county council or equivalent (whoever is in charge of schools & education in your area), they'll be able to signpost you. Alternatively you can always do this via distance methods (ie. mainly online, these days), eg. via the National Extension College http://www.nec.ac.uk, I think their fees are of the order of £500-600 per course.

PS: I can't help reiterating what ss_mel says, media studies especially is considered probably the softest A-level subject after general studies, so it's difficult to see why you would go to such effort to get a qualification that is next to useless?

It depends on the college.

Those two courses are generally seen as pointless; why are you looking to take them?

Do you plan to attend a sixth-form college which offers both these subjects full-time? If so, check their website and/or prospectus, as the fees should be listed there.

If, on the other hand, you're interested in distance learning and/or online study, InterHigh Sixth Form College offers A Level Media Studies (but not A Level Creative Writing)

http://www.interhigh.co.uk/key-stage-5-curriculum/

According to the website, the fee for one A Level is £1,100 plus registration and examination fees.

A Level Creative Writing doesn't seem to be readily available as a distance learning course, nor is it offered at that many sixth form colleges - you may need to search around all the colleges within commuting distance of where you live to find one that offers it, and it's likely to be a daytime course rather than an evening one. Have you considered taking a more widely-available option like English Language or English Literature instead?

Good luck with finding the courses you're interested in, anyway!