The information in 1881 is particularly helpful as it shows the situation before modern population movement had any great effect. It is interesting, however, to note that in most cases the change from 1881 to 1998 are not great!
While this information can give clues as to the origin of a family, it should be treated with the usual caution; fine differences in spelling has a marked effect (see for example Paterson and Patterson below) and your family may well have originated in totally unexpected places.
On the other hand some families are so narrowly distributed, there can be no doubt that this place was their 'ancient' origin. This shows up with English names such as Bickmore (Essex) and Bothway (Lincolnshire) and some of the Scottish names, MacKay, Matheson, Munro (Sutherland). However we know that the Josselyns first settled in Lincolnshire in the 11th C. whereas the map suggests Essex (where we know some lived as early as the 13th C.) or perhaps Suffolk and so the need for care in interpreting the map is obvious!
At the end of this page I have included some historical maps to show the nature of early settlement. The map of England at about 1000AD for example shows that ancestors in East Anglia (especially one like the Bickmores and Bothways) may include Viking ancestry. As Norman Davies points out in "The Isles A History" - a must read History of the British Isles (1999 - ISBN 0 333 692837) - the various invasions of England - Viking, Angle, Saxon, Norman - were in insufficient numbers to have displaced the existing Celtic populations and so probably displaced the local population's culture rather than the people resulting in mixed genes.