@woozle Thanks for your reply. It looks like this is sorted now but I will explain incase it helps someone else later on. When the computer is wired into the 4220 via ethernet and the 4220is also...

I have an existing powerline network with 2-3 4010 units. One is plugged into the router, the other is two floors up and it usually works fine. Occasionally another 4010 is added and that works fine....