Hi Iain, an old topic maybe but still very pertinent.
I was in Swansea from ’68 to ’74 and almost turned down my job at Metro in ’74 to stay there to be on SS – when it launched 80% of the DJ’s were from the Swansea Hospital Radio Service -they ALL knew about radio/ music/ jingles, and it had an incredible weekly ‘reach’
The jingles were superb, and the result of Terry Mann pushing EMISON all the way. I had a copy of these just days after they were delivered 
Serie 2 was put together by the same team but Terry had most of them re-sung as he was not happy with the vocals, and they never again got the same vocal sound as series 1.
Terry Mann could tell you a lot more about it all… He’s still in radio, running a community station in the Welsh valleys in South Wales.