Rage - the basic message here you are getting is that UNLESS you run only the router directly from the master socket with NO OTHER connections you will not be able to diagnose your problems. If then the broadband drops at the same frequency you need to contact your phone provider/ISP as you have a line problem - there is nothing else in your house that could be affecting it.
Assuming that checks ok, you could start restoring other connections one by one and see if one trips the broadband.