Well its impossible that the Dutch/Belgians/Hanoverians did not take a huge part in Waterloo
The Dutch, Belgians and Hanoverians made a solid half of Wellingtons army. A good portion was also Highlanders, which leaves not many English soldiers.
There are books enough about this, going both ways. The Nassauers did a good job, espec. on Wellington's left, those commanded by their stupid prince were shot to pieces almost before the battle began. The Scotch had a problem as the Black Watch was cut to pieces at Quatre Bas.There there was this part of the Dutch cavalry that broke at the first encounter with the French and rode all the way back to Bruxelles to tell that the battle was lost.
Probably it was very much like the football match last evening where the French underrated the Swedish and in their arrogance were punished (Sweden-France 2-0). Without respect for Wellington's riffraff, they lost a battle that--as some says--could not be lost.