http://www.wemausa.com/index.htm I found these people most helpful when I wanted to replace the sender in the holding tank of a Broom 33. A US company but they do have a UK distributor but can't remember who. They will confirm. 1st measure the depth of tank and at what point you wish the guage to start operating. They can calibrate accordingly. Incidentally their senders are much better suited to "holding tanks".