We got a new TV set for this. Still black and white, but a larger screen and 625 lines. An upgrade from 405!
It had four push buttons, even though there were only three channels. I’m presuming it was in case ITV added a second channel as well?
For both a planned ITV-2 channel (eventually arrived in 1982, of course) and also for a second ITV region for those lucky enough to live in an overlap area (there was often quite a difference between programmes on, say, ATV and Anglia, or Southern and Westward).