Thanks for the responses everyone, it has given me some ideas. The official line from the Transport Department is that the suspension can be reused but not the chassis. I'm thinking replacing the draw bar and regalvansing would allowing me to claim it as a new build. I just need to have a look at it and decide how difficult that is going to be. My concern, as others have pointed out, would be doing the build and then not being able to get it registered, though looking at what others have done it doesn't seem an impossible task.
Cheers
Leachy