You've picked a quiet weekend to make your first post, Ian. Most of the English, and the Cloggies are at Stafford.
Tracing the service history of individual vehicles is, in most cases impossible. The most detailed information on this aspect to be found on any military vehicle website is provided by Rob van den Brink's WD Norton site (well worth a read for anyone interested in WD motorcycles) :-
Basic information such as contract numbers and dates etc. can be ascertained by reference to the Orchard & Madden 'British Forces Motorcycles' bible, filled in by subsequent research. The 'O&M' book is pretty much essential if you're serious about the military usage of these machines.
Personally, I'd prefer to see photos of engine and frame numbers before going into detail on contracts etc. All too often, numbers have been incorrectly read or worse, re-stamped. As Douglas points out, the numbers you have quoted are not complete. The numbers on military M20s should have a KM or WM prefix. Engine and frame numbers originally matched.
There were some RAF WM20 contracts but as with RN, these were finished in standard service colour during wartime.
Hi was this the bike listed on eBay, possibly a 1945 bike. Do the numbers have W before them. Just had a look had a look in British forces book, if I'm right the engine number seems to be from contract C11101 and date 5/7/1941-42, order originally for 350cc OHV? Can't find info on the frame, if WD I could possibly Be under contract S9330. Get some pics uploaded and these guys will give you bit more info.