You could try and start off getting some work experience for a local radio station. A lot of people start this way. Eventually you could have a go at reading the travel report, which could progress to the news and weather or more. With this under your belt you could offer to go and work (for free) in a local TV studio newsroom. Make a showreel of your voice, doing different things (ie- a couple of minutes of each thing) and send them off "on spec" to TV production companies (the ones that specialise in documentaries etc). You could also get a qualification in Media Studies, where you would learn some skills and may make some useful contacts. These sorts of jobs are rarely advertised- you have to go and seek them out!