[Neil Jones]

The intention was to make the episode lengths consistent wasn't it, so they could fit rigidly in their clockface schedule (always meeting the top of the hour, even if it meant padding every flipping double bill of 1 vs 100 with a matching 5-10 minute Auntie's Bloomers to fill the gap) and consistently have the longest breaks possible.

Yes, and it affected BBC programmes a lot I remember as well. Paul Daniels Wipeout was totally shot to pieces so it could fit in a 30min slot with adverts. Normally it would have been 40 minutes.

For stuff from the commercial networks there would have been less to hack out, as it would have already fitted a 30min transmission slot, but as you say it was probably to squash it into 25mins and trot out Auntie's Bloomers or a Beadle's About segment.