You could become a lighting technician by qualifying as an electrician and get practical experience in production lighting.
To qualify as a lighting electrician, you will need the City & Guilds Certificate in Electrotechnical Technology and relevant practical experience.
You could take the City & Guilds full- or part-time at a local college. For work experience, you may be able to find a traineeship with a specialist lighting company.
You could also look for experience in the following settings: lighting equipment hire companies; BBC work placements (competition for these is very strong); theatres or concert venues; amateur theatre; student or community film projects.
Contact Skillset Careers for more advice about getting into film and TV lighting.
It is a good idea to make a 'showreel' DVD of productions you have worked on, to show your skills to employers when looking for work.