This was a kids’ movie I saw on CBC in colour in the mid to late ’70s. It’s probably British (based on the setting of a pivotal scene described below) and aired on a Saturday morning.
The boy can travel to places via his TV when it’s tuned to static. I think he was guided by a man in the TV wearing skis which, I guess, helped him navigate the airwaves, though this may be a memory from an entirely different film.
The scene I remember quite vividly is after the boy has been captured by guards in a castle — possibly beefeaters in the Tower of London — and ordered to be executed by beheading. He’s granted a final wish at the chopping block and asks to watch his favourite TV show. So a TV is brought over and placed before him and the guard, sympathetically, asks if he’s enjoying the show. The boy replies that he is, although there’s nothing but static on the screen. At that moment he disappears into the TV and makes his escape.