Ok, I've got it. User error compilation. Incredible. 
- I marked up all my resistors and the 10M? and 1M? were the last 2.
- My 1M? uses a colour to denote 4 that's much more like a green than a yellow. So I had them down as the 10M? and thought the others were the 1M?, and used those values. But on top of that,
- My multimeter's highest ? range is 2000k, and 10M? is 10000k. So the multimeter can't read them on any scale, hence no reading (I think!).
- When I tried to work out why the 10M? wern't measuring I re-examined the scale and saw the 2000k max.
- Lightbulb moments followed once I realised 1000k = 1M?