The location used for Oz and Uli's picnic is Tyke's Water, near Elstree, used many times in TV and film - notably The Avengers The Hour That Never Was (1965); You Have Just Been Murdered (1967) and They Keep Killing Steed (1968)
The scene where Oz is lying on the bed with is hands behind his head, exposing his bruising on his right arm, this was caused by an injury from the previous episode whilst filming.