A BTEC which is "equivalent to 3 A-levels" is called a Pearson BTEC Level 3 National Extended Diploma. This qualification is widely accepted by universities. However, as you've alluded to, they will often request that the subject of the BTEC is relevant to the degree for which you're applying. Hence the subject can be important (but isn't always).
Colleges are often very creative with the titles
they give to the BTECs they teach (which often differ from the official names), in order to make them sound more appealing or more relevant. What you need to work out is
exactly what the subject is. It is not "Media Business" and is it not "Media". We know that because no such BTECs exist. The full list of BTECs can be found
here (click the "Expand All" link).
Your college might be teaching one of the following BTEC subjects, which are related to business and/or media and/or marketing:
• Business
• Creative Digital Media Production (this has pathways named "Film, Television and Radio", "Interactive Publishing and Media" and "Digital Games")
• Creative Media Practice
• Enterprise and Entrepreneurship
• Marketing
Now, having said all of the above, the following marketing courses at what I'd consider to be "good" universities (for Marketing)
don't actually care what the BTEC subject is. There requirements (as listed on their respective web sites) are:
• Marketing BSc (Hons) at
Lancaster University: BTEC Distinction, Distinction, Merit (
source)
• Marketing and Management BA at
Durham University: BTEC Level 3 National Extended Diploma/OCR Cambridge Technical Extended Diploma – DDD (
source)
• Business with Marketing BSc (Hons) at
City, University of London: BTEC: DDD (
source)
Those are probably all in the top 5 or 10 for Marketing. So it's seems that the subjects isn't so much of an issue after all. (Although you should still find out what it actually is.)