I chose Carlton for the surname of the hero in my sweet Regency novel, Tuesday's Child. However, when I went through the characters in Sunday's Child I remembered that the heroine's title is Lady Castleton. I heaved a very deep sigh and consulted Burke's Peerage in a final attempt to find a surname. After much a time consuming search and much thought I chose Markham.
I can't begin a novel until I have named the principal characters, so, another deep sigh, this time one of relief because I want to begin work on the character profiles.