Grumpy Gnome I feel your pain!
Here are (some of) the Brittania Congo Jeep figures next to a 28mm knuckeduster figure. These are the biggest driver figures out there, believe me I have looked. Please ignore the bad half finished painting!
Here is a Dinky diecast scout car which is 1/48 and two of the Britannia crew figures, one with a Chiltern Brit head. They had to be modified slightly to fit inside. Alongside is the torso of a Chiltern Brit Desert rat
A standing Chiltern Vietnam guy, with the 28mm mini and the driver again for comparison. He is 35mm tall to top of head, so I call him 1/48. I think he works well with the 1/48 vehicle.
Hope this helps.
The Britannia jeep crews can be bought without the resin jeeps if you ask Andy Grubb nicely.