1950 saw Ambassador fit their own rather weird tele fork. Once seen, never forgotten. The bike is known as the Series V (flash Roman numeral for 5). They then went back to Webb pressed steel girders for a final year in 1951. All easily identified from the frame number.
The main guru for Ambassador info and co-author of A Guide to Ambassador Motor Cycles is Michael (Mick) Easton. In the Guide he gives his contact for correspondence as ambassadorguide@googlemail.com and his postal address as c/o 4 Low Croft, Wolodplumpton, Preston, Lancashire, PR4 0AU, UK.
If these have changed I'm sure the British Two Stroke Club will have a current contact as Ian advises.
A very willing bike is the 6E powered Ambassador. It'll quite happily take you anywhere you want although not quite as fast as you'd hope. Not fast but powered by ponies with very sturdy legs.
Cheers,
