If you are going to include populations, rather than figures.

The medieval scots. William Wallace's lot where not unwashed hairy barbarians. They were civilised, hosen wearing, french speaking, hair brushing, shield carrying people just like the rest of north western europe. Nor did they go about following random peasant folk into battle purely because they could shout the inspirational word of the day loudly.
You could more or less extend that to any small european populace. Welsh, Irish, Scottish, Cornish, Finn, Bretton, Belgian & manny others get treated rather badly by modern media.
The History of the Welsh, according to Pop-Culture:
(Views are not my own and are not supported or endorsed.)
?-? DRUIDS!
Circa 400- 600 Wales suddenly pops up as the derpy part of mainland Britain.
600-1415 Wales continues to be derpy. Rebelled a bit, ran away.
1415- Welsh soldiers briefly become crazed murderous killers who don't take captives and kill lots of Frenchmen with magic armour piercing bows.
1416-1484 Don’t exist.
1485- Opinion split: 1) Snuck one of their own onto throne. 2) The sneaky Lancastrians cheated and stuck a man [who may have been welsh] onto the throne. 3) England ran out of nobles so sent out for an English/French/Welsh bastard.
1486-1878 Derped about. Had a riot about expensive prostitutes, ran away.
1879 - Sang while killing hundreds of Zulus in a boring film which is on too often at Christmas.
1880-2013 Derped about. Drank tea. Provided token silly people for sitcoms. Complained when the mines got shut down.