Try www.thetford-europe.com
The also they cover downloads of installation manual/instructions as well in same area.
Follow this for instructions on repairs and somewhere along the way you will see installation instructions.
HOME PAGE SELECT ENGLISH
NEXT PAGE SELECT CUSTOMER SERVICE (tope line)
NEXT PAGE SELECT USER INFORMATION (left of pic)
NEXT PAGE SELECT REPAIR INSTRUCTIONS (left of pic)
NEXT PAGE SELECT BUILT IN TOILETS [top right of pic]
NEXT PAGE SELECT C2, C3., C4 (or relevant) or select your model
NEXT PAGE PDF Files YOU ARE NOW IN PDF FILE LIST
Nobby
April 2009