One thing you need to know is that there are currently very few programs broadcast on Freeview HD that actually have 5.1 surround sound! But the big issue I have is the BBC HD channel (and 4HD) flag everything as 5.1 even if it is just stereo!
This means you end up with your surround system just outputting most material from the right and left speaker, with nothing coming from the centre. Since it is incorrectly flagged you can't switch your surround amp to a suitable Pro Logic mode (pseudo surround) to get the correct output from the centre speaker.
This just adds to the already big mess that is Freeview HD due to the adoption of AAC for the sound over the standard Dolby Digital (and the new Dolby Digital Plus that would have given the required audio descriptor service required by those with sight problems).
I bet most who have Freeview HD decoders don't even realise they never have 5.1 surround sound! (A quick tip, look for the light on your amplifier that indicates digital surround sound, mine is blue.)
It is time for magazines such as yours to start a campaign to get the Freeview consortium to sort this mess out. Even if it means switching to Dolby Digital at this late stage.
While your at it get the BBC & 4HD to either switch to stereo on the HD channels when the material is only stereo or encode the stereo with Dolby Pro Logic so I get the correct surround sound from my speakers!
Currently they keep transmitting 5.1 no matter what the source material, so you end up with sound only from the right and left speakers most of the time! My amp (Sony STRD2400ES), like many others, can't use a pseudo surround mode when it detects 5.1 over the HDMI connection. (Why should it as the signal indicating 5.1?)