I think this one is going to be a cable fault After the testing above I also invested in a cheap cable checker ( can be gotten for a few £ on Amazon ) .. When I test the cable run from the new...

@Alexandre. I tried your suggestion ( and a few other related variations ) One switch in the Garden , one in the house: - TP Link switch in Garden connected through new Cat6 cabling to Xyzel switch...

@Alexandre. .. Great thanks for the advice .. I will try that later and see if that helps and report back !

Just to confuse things though if i totally bypass the switch in the house and just connect the LAN port on the main Deco straight down the new Cat6 cable to the new switch/node in the Garden building...

Further testing - Looking at the TP-Link switch in the new building .. the Green activity light on the LAN port that takes the network feed from the new Cat6 Cable faceplate connected to the house...

@Alexandre. - Yes thanks .. good suggestion I will add that to the list of tests to try and will report back !