By GEORGINA LITTLEJOHN where are you two going? Katie and James arrive back at her hotel after their party night outShe might be the sweet and butter-wouldn't-melt pop star on stage.But once the lights have gone down and the audience has gone home, Katie Waissel is just a rock chick at heart.And no true party girl would be without a DJ on her arm Katie, 24, was snapped in the small hours of the