Depends what/ where you want them for. The British Auxiliary Legion troops in the Perry Carlists for the most part aren't actually wearing British uniform, at least not British Army uniform.
Studio Miniatures ran a kickstarter for the First Afghan War, which should have British in tailed jackets and bell top shakos. Not sure what's happening with their release. If you are looking at Canada, then they are doing greatcoated versions which would be perfect.
Wargames Foundry still have Brits for the First Opium War in their old China Wars range. Those are lovely figures, Perry sculpts, in bell top shakos and shell jackets.
Beyond that there are some useable figures in The Empress Maori War range and the Perry Cape Wars range, mostly the figures in shell jackets and forage caps. Worth noting that shell jackets were really only issued in hot climates at the time.