I always imagined them to be quite big and chunky I'm surprised they are small.
Yes, their style is somewhat chunky, which when looking at the pics on their site makes you assume they are big. But in fact they are quite small.
I'm afraid I don't have any 1st Corps British regulars to give you an exact like-for-like comparison (my game is set in the Sixth War rather than the Eighth, so I went with Perry Carlist War figures), but I hope this will help.
Bare Metal

1st Corps Boers and Mutineer British command.
And with some paint on


1st Corps Xhosa and Mutineer British command.
It may not be immediately noticeable, but the Xhosa have had their bases built up a little, to help disguise any height difference (as I want to mix them with some other manufacturers in my games).
Hope that helps a bit.