It's a Prussian Kürassier kettle drummer, from one of the line regiments. This piece made me think first of Tradition, but they don't make a Prussian Kürassier kettle drummer for any regiment but the Garde du Corps. And the base is not the same, either. The bases for the Tradition kits are a flattened oval, like a race track, and raised with the rounded-over border. On looking further, it makes me think of Rylit. The bases in Rylit's mounted kits are flat, and irregularly shaped, like this one. But Rylit didn't make any Imperial German figures, as far as I know, only Seven Years War Prussians.
It's not a Rose (Russell Gammage) figure, because Rose didn't make any other Kürassiere than Garde du Corps, either.
It could be a Stadden custom figure, mounted on a one-off base instead of the tin sheet. That's my best educated guess.
Are there any markings under the base, too, that might indicate who painted it?
The facing color and the color of the kettledrum banners suggest that the painter meant to depict the Garde-Kürassier-Regiment, which was the only regiment to have that color for its facings. But they were the other regiment, besides the Garde du Corps, to wear a silver eagle on their helmets in place of a spike, for parades. Also, they had the Garde star on their helmets. This one looks like it was painted with the eagle badge with spread wings.
I have no idea about the Tommies.
Prost!
Brad