Toseland and Sefton are both classic British surnames used for these characters. Both the -land and -ton suffix were used to indicate locations, meaning "land" and "town" accordingly. Families with those surnames came from those places. Toseland was recorded as Touleslund in 1220, literally translating to "Toli's Grove." Toli being a personal name or family name. Sefton is comprised of the Old Norse "sef" which means rush and translates to "the settlement where rushes grew."
I have added both names to the BabyNames.com database!