The biggest single shake-up in UK radio broadcasting happened on 23rd November 1978 and affected all four national services. In the months and weeks leading up to the big event the BBC publicised the changes on air and in the press. Remember those stickers issued with the Radio Times to put on your radio dial? Radios 1 and 2 commissioned new jingles from JAM Creative Productions in Dallas and Radio 4 rebranded itself as Radio 4 UK.
There's already quite a bit of audio on the web about the frequency changes, see the Vintage Broadcasting site (no longer online as at Jan 2012) for example. I'll be posting a lot more, by instalments, over the next few months.
To kick things off here's some audio of the BBC tv coverage on Nationwide on the evening of the 23rd.
For the record you'll hear Nationwide presenters Sue Lawley and Glyn Worsnip. On the radio there's Kid Jensen, John Dunn, Patricia Hughes, Moira Stuart and Week Ending featuring David Jason. The Managing Director of Radio is Aubrey Singer and you'll also hear The Kings Singers. The Radio 4 newsreader, who gets talked over, is Colin Doran.
At the end of the Nationwide clip I think it's Hugh Scully and John Stapleton. The tape runs on into an announcement by BBC1 North announcer Vanessa Hill introducing Tomorrow's World.
From October 1977 here's Page 1 and Page 2 of BBC Engineering Sheet 1045 explaining the new frequency arrangements.