You do not need any specific qualifications to work as an audio-visual technician although most employers will prefer to see some experience and/or skills in this field.
You may be able to get into this job through an Apprenticeship scheme. The range of Apprenticeships available in your area will depend on the local jobs market and the types of skills employers need from their workers (see www.apprenticeships.org.uk).
As an alternative, before looking for work you could take a college course in a subject that covers some of the skills needed for AV work, such as: video or media production; multimedia technology; photography.
Experience and qualifications in sound technology, IT or electronics can also be useful for starting a career in AV work.