Yes you can be banned. Individual airline's decision.
However in your case - you are most likely classed as a minor. And if you actually leave the country, when you get to the other side there will be some questions as to why you're travelling unaccompanied. Many countries require unaccompanied minors to travel with a letter from their parents.
While you may be able to get a new plane ticket and passport, since your parents reported you you are likely to be blacklisted. And if you think you've got a chance of getting a job over here in London you're mistaken - thanks to the recession there is now at least 10 people going for every single job in the UK.