Tip: (a bit of a story and then) New laptop with a sudden loss of WiFi
Picture the scene....
Me = on an old and dated (no jokes please) W7 laptop, connected to the Plusnet Hub One via wifi 
Daughter = next to me rather than up in 'er room 
, on a brand new (well, not a month old yet, but near enough) W10 laptop, connected as above, also it was fully up to date just before the following occurred
Me = lurking on these forums 
Daughter = doing online homework, but also humming a tune.... = me 
?
Me = glances at her laptop to see online college tab, and youtube tab = daughter using headphones to do homework 
The brand new laptop suddenly lost the wifi connection to the www
Daughter = o-m-g dad! = me, no it's oh my goodness = daughter = wot evvs dad = me, sigh (ruddy text talk) = daughter = I've lost the music I was listening too (she mentioned nothing about college work!!)
Laptop passed to me:
Me = confirmed no wifi via PNH1, tried more than what most would do (not bragging, had to learn it all the hard way)
Me = try the BT Hub that's running as a slave = also no wifi too
Me = tried to connect to either multiple times = laptop showing no signal from PNH1 or BTHH, but TTrouter = low signal and VMrouter = good signal 
Me = why would it show no signal to saved networks, but shows signals from neighbouring routers....?
Me = forget saved networks, scanned again, it sees PNH1 and BTHH as 1 bar, connect to either = no connection (unable to connect)
Me = ran troubleshooters and they were pointing to the PNH1 being at fault also witnessed the err_internet_disconnected message, some may stop at that point and get on the blower to PN
Me = connect laptop via ethernet to PNH1 (lucky this laptop has ethernet available as it was one of the specs I made sure it had) = connection
Me = some pondering, a bit of head scratching and then started checking even further.....
Me = what's causing this..... = Google Chrome !! went to chrome://help/ via browser and the about section stated that the auto browser update was not moving and stuck at exactly 50%.
Me = tried to finish = error message = close browser, open again, chrome://help/ again and update finished = me phew
Me = as soon as the update finished, checked wifi signal again and all is well = me confused that chrome could even do this....?
So, if anybody finds that they suddenly lose their wifi connection to their router when using Google Chrome, see if the update for Chrome has got stuck.
Posted purely for future readers 
(note to admin or mods, please move this if it's in the wrong place)
Thanks for that suggestion, I might have a goosey at that later 
Not a Chrome user myself, tend to use a non standard FF
Daughter also uses FF most of the time, but the college insist on them using Chrome
Nothing updates on this laptop, without my say so!
I know, I wouldn't have believed it was Chrome either.
Even going via cmd (ip release/renew etc etc etc) also proved fruitless.
Tried things like flight mode too, forgetting networks etc also didn't fix it. The laptop was allocated the correct LAN IP (not 169.xxx.xx.xx), everything seemed fine bar the no signals for the saved networks and the no internet connection for either SSID's.
When it was connected via Ethernet, checking for updates was one of the first things I looked at = up to date.
I should have noted the error message after trying to finish the Chrome update, it only finished updating on the third go....?
If the laptop couldn't see any WiFi networks then I'd have gone down the route of the WiFi drivers (I updated this around 3.5 weeks a go) or the card itself being at fault. It was odd why the only two networks saved were showing their names but having no internet connection - primary router downstairs, secondary upstairs.
The W10 troubleshooters pointed to it being the router(s) at fault, I knew this couldn't be right as no other device was affected at the time.
If it wasn't Chrome, then I have no idea what else it could have been 
(should it happen again, I'll pay more attention to the error messages/codes and note them down)