UK youth interested in politics

According to the BBC: "81% of 16 to 20-year-olds feel strongly about issues like crime and education". Yet only 20% vote. This is quite clearly not apathy like the parties claim, apathetic people do not have strong views, so it must be something else. While I do vote I normally vote for one of the fringe parties, Green or UKIP, simply because none of the main parties represent my views. They are all to some degree authoritarian. They all believe that problems are best solved from the centre.