Thanks Richard / Les
Interesting that you both appear to have skipped over the teaser in my first posting - I was expecting your approval / disapproval before now. I must be more explicit in the future!
Out of interest, and to validate the answer, I've been trying to find better pictures of the Crossley chassis with no success. The best I've found are pictures of the now restored civvy Crossley BGV1 six-wheeler (The Automobile Magazine, Aug 1995, p58; and Classic & Vintage Commercials Magazine, Sept 2006, p34). But there are more differences than similarities!
What do you have in your files?