Of course the sharp eyed viewers will have spotted the obvious mistake in my config setting above.
Correct text should be (the IP in the boot line was wrong!):
dhcp-option=66,“192.168.1.1”
dhcp-boot=pxelinux.0,192.168.1.1
I can now see the device come in as Incoming, I can accept it and then it transfers the image and boots up to a heartbeat led on the MOX but the state in the managed devices screen shows an exclamation mark “!” - nothing in the documentation on this. Plus the device seems inaccessible on any of the DHCP IP addresses I see assigned to it in the syslog on the TO controlling router.
My current assumption is that I need to generate a token on the remote device and upload to remove the “!” but if I can not get the IP address then this is hard to achieve!
Comments and suggestions welcome ? 
Edit to add:
OK - from other forum posts (specifically this one MOX: how to netboot? )
It appears clear that netboot provides a ‘dumb’ device which extends your WiFi using the ethernet cable and SSID names on your controlling router and no web based presence. So my MOX is now netbooting and also extending the wifi from the TO router.