The Rachel Papers (1989)

Charles Highway (Dexter Fletcher) is in control of his life; he is about to finish sixth form college and start at Oxford. He is nineteen and wants an older woman before he turns twenty. Enter the beautiful Rachel Noyce (Ione Skye), and Charles puts his 'master-of-seduction' routines into top gear. Things however get complicated, Charles has a string of exes and a weird brother-in-law. Rachel has a boyfriend named Deforest (James Spader), and Charles' father has a mistress.