After some internet research, (bored at work this time of year) no one buying caravan / motorhome spares.
I found a free PDF which appears to be a book that has been scanned and put onto the internet in NZ.
Its called: 2-Stroke Tuners Handbook , by a Gordon Jennings printed 1973.
Very interesting read and I found it good.
Should anyone be interested I have downloaded it and could forward.
Also there is : BSA Bantam D14-4 Workshop Manual .
Or if anyone interested the link below gives the website.
http://www.custgp.com/downloads.html