I am getting a pixilated picture on BBC 1 but not the other channels. I have done a software update

[Gillhutcho]

I am getting a pixilated picture on BBC1 on my sky Q box. 
I have done a software update and thought it was better so cancelled the engineer visit. 
however it isn't. 
I do have a WiFi repeater near the tv which I thought might be interfering. However when I turn this off it doesn't seem to change things. 
otjer thoughts are the weather ???? Or that I don't have HD anymore ???? 
should I just rebook the engineer as there may be an issue with the dish / cabels