That nice man Malc Crook (https://hackaday.io/mal8837) contacted me after my last post on this (https://lamm.space/2016/09/10/presence-sensors-revisited/) to say he'd bought some sensors from the same supplier and they were different yet again.

Malc sent me some sensors to hack and return to him so I've added a new post at https://lamm.space/2017/02/28/presence-sensors-again/ with details.

Hopefully this will help some people!

Ian.