For anyone who missed this and likes their '77 Punk in video format have a look here: http://theultimatebootlegexperience2.blogspot.com/2010/12/slits-damned-subway-sect-clash-1977.html
The Clash, Subway Sect and Slits parts were recorded at Sussex University Brighton England on May 25, 1977 on a show during the White Riot Tour. The Damned and Adverts parts were recorded at the same venue on June 15, 1977.
More info here: http://homepage.mac.com/blackmarketclash/