I am currently using a ZyXEL P-660HW router (previously had a Netgear DG834Gv3 but that is now faulty and a Zyxel AMG1202 from the ISP). Only using this because RouterStatsLite works with it.
The noise on the mains incomer is picked up by the security lighting cable which runs along with it for about 3m and it gives a great signal at the light switch....!! I don't know if the phone line is picking this up as it does not run close to the mains cable(or even parallel to it). The noise is intense at the CU which is about 2m from the router, so either airborne or down the mains cable would seem to be possible.
I could ask BT to relocate the phone socket, but as this problem only started in May 2014 (we had slow but workable BB up to then) and as far as I know there have been no new RF sources in the area, I am reluctant to pay out to have this done, it might not even solve the problem.
Although we are in the country the only active farm is about 0.5 miles away, other buildings near us are all domestic houses with no significant machinery in use. The only thing that has been suspect is a new borehole pump that was installed in 2014, but the mains cable to that comes from a different transformer a long way away from ours, the pump is about 130m from us. Having said that the interference is so random and of varying duration, that it is consistent with something like an automatic pump somewhere, the problem is how to track it down and prove it, the owner is not very approachable.....! Incidentally he has switched to satellite BB to get a good service, but he has a lot more money to throw around than I do.