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 quote from the song "It's a Long Way to Tipperary" by Jack Judge and Harry Williams.