I tried connecting them last night via HDMI but the first time the laptop just switched straight off as soon as I connected it. When I restarted it there didn't seem to be any way to get rid of Windows and bring a blank screen up so I'm not sure if I'm missing something or not. I read online about it being output only but now I'm totally confused.
Your computer's HDMI socket is an
OUTPUT. It is there so you can display the computer's screen on a TV, projector, or monitor, or add a second display to extend your Windows desktop. You
CANNOT take the HDMI output from another video source (eg the HDR-FOX or any other STB, DVD player, whatever...) and feed that into the computer. At best, it won't work. At worst, it might bugger something up.
DON'T DO IT.
Honestly, looking at two connectors and saying "hey, I've got a cable that can join those two" is plain stupidity. These days, everything
should be designed not to fit where it shouldn't, or come to no harm if it can be connected incorrectly, but there is no substitute for being aware of what you're doing. I have seen plenty of cases of cables on the market that are made to connect two things that shouldn't be connected and won't work if you do, just because the unwary will buy it thinking it is the solution to a problem. It wouldn't surprise me if somebody were trying to flog a "13A three-pin UK mains plug to VGA adapter cable" (it's no more stupid than some things I've seen claiming to connect analogue video to a digital display, but obviously a damned sight more deadly).
The HDMI spec sacrifices being idiot proof for the convenience having a cable that will connect either way around. However, the basic concept is to connect
one video output to
one video input. There are no variations on that theme.