How to connect an Airport Express through a network mains adaptor

I currently have an Airport Extreme (4th Gen) as my router and have two airport expreses that work perfectly when directly connect wirelessly to the Extreme.

I recently bought a Devolo 200 Dlan AV which is a network adaptor that also has WiFi ouput as well as an ethernet one. The idea was to run an internet TV from an ethernet cable and then use the WiFi to hotspot my office upstairs AND use one of the Airport Expresses to stream to a stereo.

Ethernet connection works fine. The TV works great. The WiFI works fine & I can see (MAC addresses) any WiFi enable device connecting to it at good speed - (100Mps). I can even see the Airpot Express connnecitng to it (either one in fact).

HOWEVER trying to connect the Airport Expresses to the network and actually use it is almost impossible. I have twice managed to get the Airpot Ulitity to connect them all up just as I wanted but then is drops and cannot find the AE that is trying to connect through the Devolo 200 wireless adaptor.

I get an error (-6753) but cannot see any useful comments about sorting it out. I know that each piece of kit works its just getting them all talking to each other that is the issue.

Any help greatly appreciated. Its driving me crazyz know it 'nearly' works!!