Genrally they refer to divisions, and units are left – it would seem – somewhat abstract, but are referred to at least once as being brigades. However, The Peninsular British lists specifically state that the British armies represent Bragades, with units as Battalions; but also state that this scaling has no effect on the game.
In short, you decide. The army lists represent a Division, or A Corps, it is only the wording that changes in the mind of the reader.
I will play at the Divisional scale, with the individual units as battalions/regiments within a brigade; three or four brigades forming the tabletop division.
The are holes in the rules you could push a French Column through, but they are resolveable, and I think the game can play well