My google page speed stuff I had been doing to speed the page up had broken things. One of the page speed rules is "move all your scripts to the bottom of the page", and it is scripts that was serving the ads. I was doing this automatically and had not spotted it. Fixed now!
Paul Clarke's blog - I live in Hythe in Kent. Married + father to two, I am a full-stack web engineer, + I do javascript / nodejs, some ruby, python, php ect ect. I like pubbing, running, eating, home automation and other diy jiggery-pokery, history, genealogy, TV, squirrels, pirates, lego, and TIME TRAVEL.