Sarah Michelle Gellar and David Boreanaz practiced with sword-fighting instructors and did some of the fighting themselves, but it's clear that the stunt doubles do most - if not all - of the wide shots.
When Buffy tells Angel to close his eyes at the climax, the song Close Your Eyes, which is Buffy and Angel's love theme, is playing on the soundtrack.
Spike's description of the end of the world as "goodbye Picadilly, farewell Leicester bloody Square" is a paraphrase from the song "It's a Long Way to Tipperary" (1912), written by Jack Judge and Harry Williams. The correct/original lyrics are: "Goodbye, Piccadilly, Farewell, Leicester Square!".