Channel 4
The first image shows an early Channel 4 clock, dating from 1985. The second image is from ten years later, and shows a slightly different clock transmitted as Channel 4 closed down for the night one evening in December 1995. Two years further on and the station is 24-hour.
A rather unusual Channel 4 logo.
Finally, here are two Channel 4 break bumpers: one from December 1995, and one from December 1997.