Just to say thanks for the 'aerial out until half way through' retuning advice, 8009514. All my Freeview problems have been solved. I no longer have two channel fours; the channel 4 I have got is the correct one, i.e. not S4C (which I had after a 'conventional' retune earlier today (to try and get rid of the problem)); and the EPG is now showing complete listings for all available channels (rather than half of the channels showing 'no information available). So, all in all, I'm a happy chappy. Cheers.
Now I've just got to sort out my sister's Humax box...
Now I've just got to sort out my sister's Humax box...