Thank you – yes; software updates are delivered via the Internet and, as I said, let us not rule out anything in our on-going quest for reliable TV reception at RQ! 🙂
I did unscrew my wall plate as soon as I suspected its role in the sudden loss of signal, which is how I discovered the cable 'kink' inside and its potential significance:
Basically, I understand the 'kink' in the cable may reflect and bounce back certain frequencies, resulting in some frequency ranges distorting or cancelling out and in some channels pixelating or disappearing (which might explain the frequent reports in here of some, but not all, channels affected).
The cable enters the wall plate from above but connects inside it from the bottom up, so (unless some wall plates were originally installed upside down) this would affect the whole of RQ as a faulty (or at least as a non industry-recommended) original installation, as per the link in my previous post.
More reading here: http://www.satcure.co.uk/tech/kinked_cable.htm