This one has me stumped.

About 2 months ago I moved to a new house in Morrinsville and the internet runs on VDSL.  No problems there.

About a week after I moved in both the WiFi routers stopped working  saying no internet connection.  After various reboots  nothing so left it over nite and next morning all was good again though I did turn the Spark WiFi off on their router and just used the TP Link

To day it did it again.  The 6 year old TP Link in the lounge  kept saying no internet.  This unit runs  via Ethernet  over power.  Took the TP Link into the office and connected directly.  After a few minutes the same thing. 

Turn it off and turned on WiFi in the HG630B.  After about 10 minutes the same thing.  Power off and on the HG unit and all seemed to be well , speed test was 30Meg  but after about 10 minutes it had dropped to near zero and Speedtest app on my phone now says "Network communications Issue"

This has got me completely  wacked.    It's almost like there is something else interfering with it but looking at a WiFi analyzer app it only shows my router and some of the neighbors  on  low strength and different channels. It shows my router at -28db

Any ideas would be welcome

Thanx in advance..