Edgar's Name Pages has two popularity charts for England going from 1250 to 1981. It includes 1700 and 1800 on it, although nothing in between. But long as you're characters aren't babies, they should've been born in the early 1700s and thus more or less covered by the 1700 list, no?
Female: http://snipurl.com/b86qMale: http://snipurl.com/b86o.
Miranda
"Multiple exclamation marks are a sure sign of diseased mind" -- Terry Pratchett