<This is not a question - it is a confirmation>
Ahmed (Thanks Ahmed!) confirmed that Firmware Vs 7 needs work and appears to have a problem with WiFi as primary LAN.
As per Ahmed's recommendation, I have downgraded to release 6.08.3 and I can confirm that the WiFi client can now be set to be the primary WAN. I have tested by turning WiFi off and the RUT switches easily to Mobile and back again when WiFi comes on.
You have to first move the Wireless link to the top and then you will be able to scan for the local AP you want to connect to. (do this under Network >> WAN)
Once done, all is good
Reference here too, but older firmware