The song played at the Greek left-handed bouzouki player's funeral (second in order at the start of the movie) is Misirlou, a song of numerous covers and versions in discography, famously appearing in the Pulp Fiction soundtrack, amongst others.
Eddie Marsan and Joanne Frogatt both appeared in Filth which was also released in 2013.
Joanne Froggatt appears as someone whom works in a dog's home, the same position she later played in Angela Black.
Eddie Marsan is younger than the character he plays. John May was born in 1966 or 1967. Eddie Marsan was born in 1968.