I dont need to prototype most of this, it's pin connections and a mosfet circuit I have used before. But the loudspeaker / buzzer and it's single-transistor amp did deserve a test before I cut a PCB. 

This has duely been breadboarded, and works rather well (It's a suggested circuit on a number of electronic design sites). Loud enough to be heard across a shop if needed.

Next step: make the Mk1 board.