Hi Tom_L

The short films were in fact officially sponsored by the UK Government. During the 1970's there was only three TV channels on TV. Two of the Channels were BBC1 and BBC2, both being funded by the government and there was a commercial TV channel called ITV (ITV being funded from commercial advertising). There was no TV broadcasting until around 9:00 AM and the TV closed down around 12:00 - 12:30 midnight. Most of the films were actually broadcast by ITV during the commercial breaks. The longer films were shown to children at school.

The Charley series of PIFs were some of the most memorable.
http://www.youtube.com/watch?v=nF9T7dcelKM
http://www.youtube.com/watch?v=3B90HxLOpes&mode=related&search=
http://www.youtube.com/watch?v=CUMcqfd8NLg&mode=related&search=

The films such as Threads and When the Winds Blow and The War Game were not sponsored by the Government. The film 'The War Game' was first shown in the mid 1990's thirty years after it was first filmed.