Hannover DeWitt's

While looking for my military ancestors I found 4 DeWitts,all officers in" The Kings Own German Legion" a British army unit who fought at Waterloo.Is there anyone who know of this family or who could point me to where to look for census (early to mid 1800's), election rolls.or any other material that would lead me to this family.The officers all had several first names which makes me think that they were upper middle class people. I have a picture of one of them, and he looks like a country gentleman. I look forward to all replies. signed TuiS (NZ)