Some of the Shermans in A Bridge Too Far were GRP hulls on top of Beetles. They were kept in the back of the long road sequence so you can't notice that the tracks don't touch the ground and the four wheels beneath them!
I've never quite worked out what Michael Caine's scout car is, looks like a Humber Mk.I scout but with a non-standard roof.
Guns of Navarone was all US kit (M24s, M3s, 105mm guns).
US war films made during the war often used M-2 light tanks or early M-4s to stand in for Japanese tanks. I think its Fighting Seebees that has a dodgy wooden replica with a wobbly cardboard gun that gets rammed by a bulldozer into a ravine. Sahara has M3 half tracks for the Jerries (the 1980s remake does too but at least adds an MG42 - still wrong time period though).
Period British warfilms often used British kit with the Balkankreuz added; Humber/Guy armoured car in One of Our Aircraft is Missing, a Cromwell tank crops up in another 1950s film, its surprising how often the Covenanter tank crops up, clearly training units were drafted in for these films.
Its quite laughable how some of the filmmakers liberally spray British vehicles with numerous giant Balkankreuz to try and convince you they are the Germans (on doors, bonnets, the back, the roof!). Sea of Sand used US M3 halftracks for the Germans, some tanks are found but only seen close up in the dark and are probably Cromwells/Comets, a German armoured car also appears which looks like a British type (Humber?) but has a fake turret added. Generally films based in the desert used a lot of stock footage, fair easier in the days of black and white films to splice that material in.
They Who Dare had a Dingo with a taller superstructure as an Italian armoured car, the Italians also using Oxford lorries (some lovely genuine Lebanese Air Force SM.79 Sparvieros though, including two airworthy ones). There is a 1943 film (the name escapes me) with an Italian armoured car that gets knocked out with a Boys rifle, its clearly a prop job and looks like something out of the 1920s! Luckily the plucky brits find a stash of wine and a huge cheese stowed in the engine compartment!
Finally, must make note of the 1946 film Theirs is the Glory about Arnhem. The film was shot right after the end of the war, the locations are genuine (and still battle scarred), the actors were real Paras and servicemen who had fought in the battle and genuine kit was used. There are at least two Panthers in the film, one of which was moving and seems to have had a working gun too (firing blanks of course). I assume they were made operable by the Army. I wonder if this is the only war film to ever feature genuine Panthers and what happened to them after?
