Richard ~~ How many over here could explain the origin of Belisha Beacon, do you think?

To knock-up here also means to wake up in the morning, especially by knocking on the door or window. Northern English industrial town councils in the 19C-early20C used to employ a man who would go around working-class areas at about 5·30 a.m. with a long pole with which he would knock on the front upstairs windows to 'knock-up' the fathers of the families, who would sleep in the front or 'best' bedroom, and would soon after have to leave for work. This official was actually called 'the knocker-up', or sometimes, colloquially, the 'knocker-upper'.

~Michael~