Network Problems - Hardware or Windows 8.1?

Sup guys,

Having a pretty frustrating time with my AW 17 at the minute. Basically whenever it is connected to the internet, either by cable or WiFi, no other device in the house can maintain a steady internet connection. Video streams drop/facetime calls drop (my brother lives in Canada so it gets used A LOT) and basically nothing will work except basic web browsing. I feel i've tried everything under the sun to work out what's causing this:

I've checked network usage on the 17 and nothing stands out as using a ridiculous amount of bandwidth
Ran multiple virus scans
Updated the Broadcom 4352 to the Lenovo drivers because they're more up to date
Check for router firmware updates
Disabled every program individually through the firewall and non of them seem to be causing the issue

If I put the laptop in Airplane Mode all of a sudden everything else works fine. I'm just about at the end of my tether with this so I thought I should consult the forum to see if anyone can enlighten me!

One interesting point that could be related; it seems to date back to when I updated to Windows 8.1. But I don't see how this could be causing such a major problem..

Thanks