The glorious Rae Earl on what to do with one's teenage detritus: As a lifelong hypochondriac, I have had a will since I was seven. Its conditions have changed over the years (I don't think my brother wants my Smurf collection any more), but one codicil has remained unchanged since 1989. In the event of my death from a horrific tropical disease or a burst appendix, my best friend Mort must go to my…