Based on the dimensions given, the Challenger tank is 1/46 scale.
The ME 109 is 1:39 scale.
The Supermarine Spitfire is 1/42.1 scale.
I would guess they're like matchbox or hot wheels, and are "box scale". Meaning they're whatever size they need to be to fit in the box, not related to each other in any way.
I would also guess that each vehicle or place will vary, so there may be some that work for you, and others that don't. But you'd need to check each one.