Home hub 5 poor video

[#1]

Hi I got fibre 40m fitted about a month ago and I've noticed that  the video quality on YouTube and Netflix is poor and seems to buffer between low quality and high quality I.e constantly changing. I'm using a home hub 5. It seems ok downstairs but on coming upstairs it's poor, never experience this before using sky 8m broadband with their hub. The house is a new build semi so not thick walls. Amy ideas. Could it be I need to manually set the channel on the hub 5 rather than smart channel?

[#2]

Many routers do seem to work better on fixed channel than auto. 
Probably worth trying out with acrylic wifi (https://www.acrylicwifi.com/en/wlan-software/wlan-scanner-acrylic-wifi-free/download-wifi-scanner-windows/) or similar to check signal strengths and possible interference.  Sometimes quite small reloaction or reorientation of either the router or the device can make a big difference to wireless strength.
What's the device?  I've heard that some devices (iPads ???)  have issues with dual band that can be resolved by giving different SSIDs to each band on the router and being clear which band the connection is to be on,

[#3]

Thanks I'll try a fixed channel. What channel, is best? It's an iPad mini 3 I'm using

[#4]

Anyone?