A lot of posts to respond to so I will do my best to respond in full. I've attached a picture of my network map with the name of the devices.
There is absolutely zero I can think of that changing to Plusnet would suddenly cause issues on WiFi.
If wired speeds are fine (they are) and the line remains in sync (it does) that shouts out internal hardware to me.
The fact that you also experience this on the BT Homehub which worked with BT leaves me at a loss.
Changing ISP and using the same modem/router can't suddenly cause WiFi issues. This is not a Plusnet issue.
The connection completely dropping is another matter.
No idea if you can set up a BQM on either of those ISP devices.
The issues started when I switched to Plusnet, nothing else has changed and there were no problems before switching ISP's. That leaves me to the conclusion that the problem is ISP related no idea how but its the only logical conclusion to draw.
What's a BQM?
Have a few different wifi channels actually been tried?
There are plenty of things that can affect wifi but will not show on a wifi analyser app. Personally I think most wifi apps are largely worthless and may well be worse than simply trying out different channels. Most wifi analyser apps just show the signal strength from each AP and what channel they are on. They don't show how heavily used each network is, a channel with one busy network will be a lot busier than a channel with several mostly idle networks. They don't show the strength of the signals from any of the devices connected to the network, just the access point. They don't show non-wifi signals / interference on the frequencies. Some people might then argue that a wifi analyser app is still better than nothing, but even that is questionable. An automatic channel selection system on an access point should have more data available to it than what a wifi analyser app has.
Noted but what else is there to use if the router doesn't have an analysis tool.
EJS beat me to it.
I'm rather confused by the above two statements, to test direct through the master socket surely you're using your router? The engineer would of used his own equipment, which you wouldn't have been able to plug into. So statement two surely using the same equipment as statement 1, but something must be different to get the different results.
In statement two are you still using the test socket? This means removing the front of the master socket and using the socket behind? When you remove the front of the master socket it should isolate all other sockets in the house, they should no longer work - if they do this will be affecting things. Hopefully the engineer would of checked this.
Unfortunately a wi-fi analyser app on Android is not going to show things that could be affecting your wi-fi, you need dedicated hardware to show that. For instance get the app on your phone, go and microwave something and see if it shows on the app. What you need is something like the Wi-Spy (very expensive) which will actually display the signal from things like microwaves, baby monitors, remote control transmitters etc. These could all be affecting you're wi-fi, especially 2.4Ghz. Are you using 2.4Ghz or 5Ghz?
Watch this video, especially from 6:28
https://www.youtube.com/watch?v=tr0AfBO1O20
One thing I'm certain of is Plusnet are not slowing your broadband just when you use wi-fi.
Well there is, but you'd need a modem that allows you to collect stats.
The engineer plugged the cable into my laptop and showed me the reading from the master socket without the router which gave 68meg. When the router was plugged in the speed dropped to 58 meg. I don't know why there would be a difference between the speed coming out of the master socket and the speed being output by the router.
According to the Engineer using the test socket is largely unnecessary if you have a VDSL faceplate fitted which I do. In any case the engineer did all his tests and is pretty certain there are no issues with the master socket at least nothing his equipment could detect.
I will have a look at the video, however, I don't understand how one day there were no issues with the WiFi and when I switched ISP's suddenly there were, with no change to equipment or devices. Also any interference on the WiFi would impact the signal quality as well as the internet and the speeds between the devices on the network but speeds between the devices is fine.
Can I collect stats on the BT Smart Hub 6 and if so what filters do I need to set.
The only reason I can think for the wi-fi being so slow is that it is set to the wrong protocol - you haven't accidentally managed to set it to 802.11b as that would run at about 10Mbps maximum?
No change to the protocol settings they are all the same as what they were. Double checked this in case I did do something by accident.
One of the easiest ways to solve wifi problems is to separate the 2.4 and 5G (I suffix the network name with the frequency). I put all the stuff I don't want cluttering 5G on 2.4 (kids things, Alexa's, cameras). The things I want to run faster won't know about the 2.4Ghz networks and won't fail over to them when the signal is poor and visa versa for the things allocated to 2.4Ghz. I have essentially the same as you with two access points at either end of the house, so there's always a 5Ghz and 2.4Ghz available. Laptops and mine and the boss' phones get 5Ghz and most everything else gets 2.4Ghz. Everything in a fixed position with an ethernet port gets a wired connection (although senior management will kill me if I put another hole in the ceiling, so I'm going to have to get creative with the infrastructure cabling).
With 4 networks being available you can deal with any internal congestion easily e.g. changing channels or promoting a device to the 5Ghz network (although I've not needed to). The only problem is when you still have a 5Ghz connection to the other end of the house - but that's fairly rare as the internal walls are brick and flicking wifi off an on sorts this. If you are dual banding the APs (like most come out of the box), you have no idea what's going on without logging in to them and checking.
WiFi bands are already split and always have been.
My 2 pence worth:
SMART WI-FI
I can confirm that SMART WI-FI (auto channel swap) is poor in my experience, every time I've tested such a feature across various routers on various connections (not just my own - which I've tested many routers on) it seems to always pick one that doesn't appear optimal? (i.e. switching to an active channel when there are clear channels on 1, 6 or 11 on the 2.4Ghz spectrum). I know someone has already mentioned that the router/hub may have more information when choosing a channel, but the only thing I can think of is RF Spectrum Analysis and I may be wrong but aren't these types of devices expensive? and therefore unlikely to be installed in a cheap ISP router?
PLUSNET HUB ONE
I will also add (even though its probably irrelevant at this point) that the Plusnet Hub One is absolutely DIRE in my honest opinion, I had 2 from Plusnet as the first would drop its throughput from 36Mb to 15-25Mb every 4-5 days and only a reboot would fix it, the 2nd Plusnet Hub One done the exact same.. I resolved this by using my own.
THROTTLING
Your 100% not being "throttled" by your ISP, there is no way for an ISP to manipulate what goes on in your internal network, also what gain is there for Plusnet to pump 65Mb down to the router and then to throttle it and cause you issues at your end? it just doesn't make sense and can not and does not happen.
NTE5C+Mk4 SSFP
There are loads of bad reviews about these, I myself just 3 days ago tested various SSFP's/setups including the one you have even after hearing this as I wanted to find out for myself, I had loss of speed (2MB) and errors went up 10 fold (and strange readings from DSL-stats), you would have been better leaving the NTE5A and Mk2 SSFP in to be honest, its looks nice, but is cheaply made (no circuit boards, just metal strips) in comparison to the older one
CONCLUSION
After reading your thread I have to say that it sounds like its an internal configuration issue or the device(s) your testing have issues. You mention having switches and routers etc, maybe if you could supply more information about your setup and the devices connecting to it?
What routers/switches do you have?
How are they connected?
How are they configured?
Same again for devices.
- sometimes a mockup drawing in paint or a photo can help.
I don't use the smart WiFi because it was poor originally.
Switched the modem to the Smart Hub 6.
That's the only conclusion I can draw - When you have eliminated the impossible, whatever remains, however improbable, must be the truth. The only reason I can think is because of heavy usage.
I hope I have covered everything here.