Try Swift they may give you a wire diagram and also tell you what else like an MCB and what type of charger and battery to use. A car battery is false economy so don't use one for cheapness as they don't like the continual charge / discharge. If you do a complete wireup job then get it certified by electrician for insurance they may insist you do
Swift Caravans
Dunswell Road
Cottingham
East Yorkshire
HU16 4JX
01482 847332
bob
April 2011