Caravan pumps are not rated for continuous use - don't waste your money. Fuel pumps give up quickly as well - don't waste your time fitting one every couple of months.

Look in Yellow Pages, or on the net - the one I use is made by LVM, and the model is called the "Nile LVM107". It's 12V, 2.5A max, 12litres/min, rated for continuous use for 10000hours for water (and diesel). It looks like a large caravan pump, but the good thing about it is that it only cost about £45. I bought mine from Central Pumps, Derbyshire, phone number 0845 580888.