The Rachel Papers (1989)

Poised to attend Oxford University, 19-year-old Charles Highway (Dexter Fletcher) decides it's high time to have a romantic encounter with an older woman. With the help of a computer program and several eccentric relatives, Highway sets his sights on seducing Rachel Noyce (Ione Skye), a stunning American in her 20s. However, Highway has his work cut out for him. Noyce has a boyfriend, DeForest (James Spader), and is not exactly receptive to Highway's advances -- at first, anyway.