I don't have the actual construction manual, but I do have a copy of Marine Modelling magazine, March 1994, in which Charlie Pearson did a write up on his construction of the Navigator, it runs to six pages and has loads of colour pictures of his build.
I used to live next door to guy named Dennis Ursell who built the Navigator radios under licence from Brian Young of Kingshill, if Dennis is still there I'll pop round and see if he can be of any help.
If it's any help to you, I can photocopy the article and post it to you? I don't possess a scanner, so it'll have to be a photocopy.
Rich