Where (roughly) do you live? (Or do you know which transmitter serves your area?)
There's a programme of 'frequency clearing' going on with Freeview throughout this year, affecting different transmitters on different dates (and with not all transmitters affected). So, depending upon where you live, it's quite likely that you'll need to do a full re-tune on your telly (or any other relevant device, such as a Humax box) at some time this year.
In particular, anyone receiving signals from the following transmitters should have carried out a full re-tune on Wednesday of this week:
Sudbury (serving parts of Suffolk & Essex)
Tacolneston (serving Norfolk & parts of Suffolk)
Waltham (serving much of the East Midlands)
Mendip (serving Cirencester area only, with other areas served from Mendip not affected until 27 Feb)