I can't see how they could block a pc using HDMI outputs as more and more monitors (especially the 4k types) require the pc connected via HDMI and I honestly can't see how sky could detect where the output is being streamed to. If they have blocked it then use a streamer (like splash top streamer) to display the screen from one computer onto one connected to your tv.
I recently got sky and was getting phone calls asking why I had not activated my free 2 month trial of Sky Go. When I told them I would only use it on my iPad and as that is jailbroken Sky have deemed I'm not allowed to have sky go on it. I asked why (the reason is because once jailbroken you can hook the output up to a TV apparently) and none of the sales advisors could give an answer