Thanks for your reply and I have no reason to doubt what you are saying but in the accompanying manual there is no reference to recording exclusively from Freeview, it simply says a 'Digital Broadcast' is necessary. Why would Sony omit to say that you cannot record to USB if you have digital cable or a Sky STB (both are connected via HDMI).
I would want to because I have a cable HD box and not a Tivo. Tivo allows you to record, a cable box doesn't.
I bought the TV on the strength of the adverting blurb, which says 'record to USB from a digital broadcast'. This is obviously far from the truth. Why don't Sony make things clearer?