Depends really, Poole and Bournemouth college do electrical courses which you could do in the evening and will take a couple of years. If you just wanted to do a domestic installer course then there are plenty to choose from, Southampton have ATL which will offer short courses and could see you qualified to work within domestic installations within 6 - 12 months but cost a lot and there is a suggestion that you will need more qualifications to become a qualified supervisor making the only option a college course.
My advice would be to go to college and find work as an electricians mate and learn the trade that way which is great if you have a family friend to help you out. study and pass your City and guilds 17th edition exam (2382) I took a domestic installer course as it is my hobby and a sideline for me, I intend to start at college and complete my 2330 and later my NVQ. I have learnt that this industry can become very expensive with courses and people who sell you things that you don't really need. Taking the exams at college is by far the cheapest option. There are loads of great threads on this forum of how to start etc...Good luck.