I don't know who made them, but I've just been reading The Buzz on their website: http://www.bbc.co.uk/southerncounties/local_radio/the_buzz_newsletter.shtml
It does mention the jingles on it. Below is what they say about the jingles:
To go with our name we have a brand new sound to what we do.
There will be new jingles and musical beds for all parts of our output and from the end of April you'll hear catchy new sung jingles to support what we do – imagine “BBC Surrey” sung!
And brilliantly, we have two new voices for this work, Sussex girl Sara Mendes Da Costa and Nigel Williams from Surrey.