I have a couple of suggestions of existing ranges and one out of left field.
First off, the Falcon ranges are not OOP, they are available from Caliver books. Look under their 28mm listings. I have been sampling a few, they seem to vary a bit from range to range, but all are smaller than modern ranges. I particularly like the zouaves and the colonial troops with fez, they are charming.
Parkfield Sudan range. Small and slim. Use as is or green stuff the puttees into gaiters and paint them as redcoats. If the heads are a little big you can swop them for the Empress spare (zulu war) Brit heads which are smaller and neater, they look perfectly proportioned then.
OK, the wild card suggestion is..plastic Valiant figures. supposedly 1/72, they look fine next to old "true 25s"