Osprey do books on Wellington's and Napoleon's Commanders.
Both British and French generals had a standard uniform, but many concocted their own uniforms, especially gaudy Cavalry Generals, and some wore very plain uniforms, like Wellington.
Effectively British generals wore cocked hats and a red long-tail length coatee faced blue with gold lace in chevrons on the cuffs, and gold bars of lace on the collar and front, no epaulettes. The undress version had no gold lace but gold epaulettes, several generals wore only a plain or black laced blue jacket, as you see Wellington at Waterloo.
What you have painted is a very neat Infantry colonel, who could have commanded a brigade, just change the collar and cuff lace.