You do not need particular qualifications to become a media buyer. However, advertising is a very competitive industry and many employers will expect you to be qualified to BTEC HND or degree level.
You may have an advantage with a degree or HND in one of the following subjects: advertising; marketing and communications; business or management; statistics or operational research; and media studies.
To find a suitable course use the course search on this site and check with colleges and universities about course entry requirements.
Your sales skills are important, so you would find it useful to have previous work experience in sales or marketing. It is a good idea to try to get work placements in advertising agencies, as a way of getting relevant experience and making contacts in the industry.
The Institute of Practitioners in Advertising (IPA) website includes a list of member agencies offering work experience, and IPA also runs a Graduate Recruitment Agency.
For more information on the advertising industry, see the Advertising Association and IPA websites.