Why does my Apple TV kill my wifi signal?

It seems at times, that as soon as I switch on my Apple TV 3rd gen, the wifi signal to the rest of the house drops down to almost nothing!? As soon as I switch the Apple TV box off the wifi signal returns. I have the standard BT boxes for fibre optic. When I phoned Apple the only solution they could suggest was to turn off the 2 BT boxes then switch them back on! While this worked temporarily, the same problem has returned.

I also find that when watching video content via AirPlay that often it stops working. This could be linked to the wifi signal dropping out.