The 1812 warrant stipulated 'Belgic' shakos for all non-Highland infantry regiments, foot guards, line, light, and rifle. I'd understood that all battalions had switched by 1815 less the 28th Foot and Mouth.
I know that in advance of Waterloo 200, the British based 95th reenactors switched to Belgics based on some pretty thorough research. (They have also dropped the ToS-type forage caps in favour of a more accurate option).