I just got an Archer T2U Nano for my desktop PC, and connected it to my BT whole home network, but my internet is Sky full fibre, and found it was very very slow. Around 15 mbps where my phone was about 120 mbps at the same location. 

I switched the connection directly to the Sky router and am getting about 55mbps which is the same as my phone is getting. 

I can't see any reason why it's slow when connected to a whole home disc and fine when connected directly to the sky router. It isn't the disc being slow as my phone was fine. As far as I can tell the discs are 2.4 ghz and 5 ghz, but don't have separate SSIDs for both.

Any help to improve the speed would be appreciated. Thanks