Copyright
Copyright is the creator's exclusive right to publish and reproduce their material (an article, picture, music, etc.). The author has the right to choose what happens with their work. In principle, you need their permission to use their work. Authors can also ask for payment for use of their work.
There are certain copyright exceptions, which make it possible to use other people's material without their permission - the right to quote, reproduction for review purposes, and educational use, for example. Of course, it is still important that you cite the source.
Are you sure that you have not violated someone's copyright with your media product?
TIP: Have you heard of creative commons licences? This is a concept in which authors make their creative work available, in a simple way, for use by others in their own work without any charge. Still using someone else's work? Maybe you will find a suitable initiative under creative commons.
More information about UK copyright law.
More information about UK copyright law for school children age.
More information about creativie commons.