As the other boys have stated the FoV and 21C (both also sold as "Motorworks" at WalMart in the USA) are 1/32nd scale. Further as staed before, there's a generous allowance as to what is "54mm" scale in figures. K&C are closer to 1/30th. Conte, many Britains WW2, TSSD and ONTC are "large" 54mm if you place them next to an Airfix Multipose, which are closer to "true" 1/32nd modeling scale. 21C figures are very close to Airfix, as are the mediocre figures from the Monogram 1/32nd scale tank series (also not to be confused with a bunch of 1/35th scale models they boxed as "1/32nd"). Anothyer source for figures is some of the old Louis Marx figures. They generally lie between the Airfix and Conte sizes. Another source of troops is 54mm lead (now pewter) model soldiers, such as Valiant and Imrie-Risely (old lines, but both still available). Personally, my primary display group has figures from Airfix soft plastic, Airfix Multipose, Marx and 21C together and they look OK. It's YOUR collection, you can work out what looks good to you or pleases you. Don't worry about what some of us compulsives think of it.
Gary