Mr Whippy apparantly started in Birmingham in the late 1950s, according to a glancing reference on this page, that shows you aren't the only person with an interest in the history of mobile ice-cream vendors... amazing stuff:
http://www.ice-cream.org/mobiling/history.htm
They're looking for info for a book on the subject...
The ice cream cone was first seen in New York in 1896, inventor Italo Marchiony earning a US Patent in 1903. Though it was independently arrived at by concessionaires at the World Fair in St Louis the following year... including Ernest A. Hamwi, who founded the Missouri Cone Company, later known as the Western Cone Company. Though, given that lots of people obviously have too much time on their hands, there are those who dispute this!