Portrayal of Ronnie
One interesting aspect of this film is its portrayal of Ronnie and Audrey. It would have been easy to make Ronnie nothing but a avatar of low mass culture for cheap laughs, and the film does some of this (e.g. Ronnie thinking Rimbaud is Rambo, Audrey asking about Mexicans in Germany). On the other hand, it resists the route of making the young couple complete caricature of pop culture ignorance. Initially at least, both of them have a genuine interest in Giles' erudition and welcome him as a friend until his hidden agenda is revealed, something they wouldn't do if they were just shallow cardboard cutouts.
And Ronnie's reaction to Giles' rambling letter was just right - you could see the conflict between on the one hand being disgusted by an aging homosexual's advances, but also flattered by the fact that an older and much more cultured and intelligent person could take an interest in him at all.