Thanks for the link and information. I think IF there is something interfering with the router et al it's going to be the unit of this new PC. The router was working well and going about its business with Win XP and my Win 7 laptop (wirelessly) and of course when I tested that with the Ethernet cable. Also I don't have a radio anyway, well only on main TV!
Well, as you know, I agree with you. If you haven't got a radio, well nevermind. I'm less convinced now about EMI, but wanted to show willing to look again for it.
I am going to try to look again at AVG I don't have the link on the PC to put up where they were saying it was stopping internet connection. Just read however that Win 8 has Windows Defender running all the time (this was said on AVG forum).
Golly, you really believe in defence-in-depth, don't you?!
Windows Defender
and AVG2013
and the router all with firewalls! You must be bulletproof!!
This link
http://windows.microsoft.com/en-gb/windows-8/windows-firewall-from-start-to-finish will tell you how to switch Windows Defender off as well. For the purposes of your next tests (tomorrow, I think you need a break!), please disable both AVG2013 and Windows Defender for the moment. I honestly don't think it will make any difference, for the reasons we have all discussed previously, but no stone unturned and all that ....
Just to say that the following happened at switch on this morning. Router on all lights. Switch PC on - screen up "Welcome User" stayed on around 3 mins. Then message "preparing Windows" came up on different screen, then online button on router went off. Stayed on that screen for 3 - 4 minutes then the metro screen came up with only 4 apps on (store, IE, desktop, file explorer) router online light still off. I shut down PC and online light came on on router box. I turned ROUTER off, switched PC on - metro screen came up immediately, put router box on again, all lights came on and internet connection immediately. 
so if I connect router first the PC has gone back to not getting on the internet - switch router off, put PC on and I can get on the internet....>>>>go figure...I wish I could.
Well, I'm sorry to say that this appears to me exactly like the 4th time that you have accurately described what you see while Windows 8 is recovering (rebuilding) itself after it has decided that it was unable to load your Windows 8 PC properly for a (different) reason as yet unknown to me. I have said this every time you have had the bad luck to see it: this
just should not be happening 
, but I don't think it is causing the router problem per se. Unless of course, anyone else can offer an alternative explanation?
In these circumstances I think you will see something similar happening on the router lights, because if Windows 8 does repair itself, then the 'Turn Sharing Off' setting that you did previously will be lost (a good thing to check to confirm this scenario - if
you didn't change it, then it must've been this rebuild!). This in turn will allow W8 to start nattering to the router again and possibly upset it.
So, really this continual rebuilding is now getting in the way of resolving the other (router) problem you originally reported. Every time it rebuilds itself it will be similar again (in most respects) to the first time you ever switched it on and saw this problem. So we are just going backwards again, it seems to me.
Something to think about, but perhaps it might be better now to have the builder fix that problem first, and then we can see what problems we are left with wrt the router. What do others think now?
But if you can get at least the two tests done (without it rebuilding itself) and with sharing, AVG & Windows Defender off, then that will at least tell us something.
However give yourself a break from this at least until tomorrow, and think it over. I understand how inconvenient it may be to have to take the thing back to the guy, but it just can't keep doing this to you.
You can always point him to this thread so that he can see all of things you've tried, and the advice you received here from others.
