Just discovered there was a 19th century bass maker in Manchester called Warburton. Any relation Paul?
Apparently "Little is recorded of this maker, however it is evident from the form and quality of the workmanship that Warburton was a professional maker and close follower of the "Master" English bass makers - namely Lott, Fendt and Kennedy. This classic English instrument could easily be mistaken for being made by a more recognised maker and indeed it is possible that a young Warburton was apprenticed to Fendt"
see
http://www.contrabass.co.uk/2115.htm
for more details and pictures of a very lovely looking bass he made