When the 'axe murderer' panics at the sound of a police helicopter, Del Boy says the line "No it's Barratt's". He is referring to a 1970's TV commercial in which the actor 'Patrick Allen' flew in a helicopter over a new housing estate by Barratt Homes to promote their cheap starter homes.
After Rodney finds the axe in the cupboard, Del mentions going 'Up the wooden hill to Bedfordshire'. This a line from a children's lullaby written by Grey and Connelly and recorded in 1936 by 'Dame Vera Lynn'.
The 2016 book entitled "The Peckham Archive" would reveal the axe murderer's name to be Charles "Chopper" Winters.