London DIY scenesters BCOS RSNS commemorate lost live music venue The Buffalo Bar in their latest single taken from their forthcoming eponymous album. The much-missed Highbury venue gets name-checked in their hymn to the grassroots scene. Backseat Mafia caught up with Abi and Carl from the band to hear all about their random Norwegian fan club, a local London legend and the anger, sadness and humour of their debut album.  Well hello BCOS RSNS! Who are you?  Abi: Hello! I’m Abi! I play guitar and sing! Carl: I’m Carl, I play guitar but don’t sing. Abi: Matt (bass) and Jen (drums) can’t come to the phone right now. How did you get…