Some of Montys vehicles are very wellknown, like the Humber Snipe.
This has been made by Airfix in 1/32:
http://www.cybermodeler.com/hobby/kits/airfix/kit_airfix_5501.shtml
Others are the Leyland Caravan, this has been made by Wespe in 1/35:
http://www.wespemodels.ro/index.php?route=product/product&path=59_64&product_id=135
And the Fordson with the mapvan, at least the caravan is available from Wespe, I thought the Fordsson used to be as well:
http://www.wespemodels.ro/index.php?route=product/product&path=59_64&product_id=1258
http://www.reynaulds.com/products/Wespe/35036.aspx
He also used a Mack caravan, also produced by Wespe:
http://www.wespemodels.ro/index.php?route=product/product&path=59_64&product_id=180
Apart from these im sure he must have had some Bedford QLRs and this may very well be the vehicle you are looking for. Plus Models used to do a conversionkit for the old Airfix/Italeri/Revell Bedford QL Portee:
http://www.perthmilitarymodelling.com/reviews/vehicles/italeri/it6474.html
http://www.creativemodels.co.uk/plusmodel_135_bedford_qlr_body_no_3_conversion_set-p-5618.html
Resicast have a very nice full kit of the Bedford QLR:
http://www.historexagents.com/shop/hxproductdetail.php?ProductCode=R351138
Several of Montys vehicles, both of the Caravans, the Humber and the Mapvan belongs to IWM afaik and if Im not mistaken they are all displayed at Duxford, photos of them can be find every here and there, just google.
Hth
Desert-Erik
Sweden
CU@C4
www.c4-open.se