I had a quick search and found out that there were in fact possibly very few new military trucks until say the Conservatives came to power again under Churchill in 1951.
http://www.rememuseum.org.uk/vehicles/mwv/vehalbn.htm
http://www.rememuseum.org.uk/vehicles/mwv/vehcomq4.htm
explains. I am pretty certain that the Ministry of Supply bought back hundreds of refurb'd military Bedfords that were rebuilt by say Marshall's in Cambridge under Vauxhall contract. Lincoln Cars Limited in Brentford rebuilt Carriers for post-war use as well as thousands of ex-WD Ford V-8s for further use. There were still some dealers that rebuilt Ford/Fordsons as well. I can imagine that British vehicles plus Jeeps were the flavour of the time, as CMPs, GMC trucks other than DUKWs and other US trucks saving Diamond Ts were deemed to be too expensive to maintain for British post-war use.
Can anyone confirm any substantive use of CMPs/CMP-based vehicles in British service 1948-50? Off-loading them to overseas Commonwealth countries presumably solved a problem and there was then no requirement to maintain them at British government expense?
This brings into mind a query as to whether Ford and GM of Canada produced any parts for CMPs/CMP-based vehicles post-war? I would have thought that there was so much stockpiled stocks that there was no need. I have read that by early 1946 Willys-Overland had stopped producing any parts for wartime Jeeps and then the concentration was on the post-war models. Magazine adverts at the time show that there was a huge amount of new and rebuilt parts and engines that were being offered by companies.