Promod do 1/50 Bedford RLs, pricey but worth it. Corgi does a civilian Bedford S that could work as a cheaper alternative with a repaint (i have a couple that I could paint up if that helps?) The Dinky ones are a tad small (1/60 I think?) but if it's just for markers...
I've got a couple of Tarv 1/56 Landrovers that would fit, but I'm leaning to 1/50 so having a go at knocking one up over the summer.
if you want air support I have a Dak and Fouga on the work bench that should be ready in time (you can get a resin version of the one from the film but it runs to £60 +...)