It may be of little help, but 'personally' I have found that 1 in. / 25mm square bases work the best for figures of this size. Thats what Im using for my Dark Age Fantasy and Wars of Empire Colonial British (none of the later have been posted yet). The exception are the Zulu's which, like many, I use the 1 in. fender washer.
Heres a suggestion, BEFORE you spend any $$ on buying larger bases, you can also just grab an empty cereal box, and cut a few 1 in. square bases to 'test baseing' with. Actually, thats exactly what I did with my british before making my final decision.
Also, when did this, I used simple white/ pva/ elmers glue to hold them in place. It holds great -for a few days- but it lets you get a good idea how they will look. Best of all being water based itself, it cleans off with just a touch of soap and water, leaving no residue at all.
"You see old friend. I brought more soldiers than you did." *Leonidas-300