Take a look at this great site spotted by Nick. All you do it type in a surname and it gives you a map of distribution and frequency of that name in 1881 and 1998:
Try it with your parents' surnames and do some instant genealogy. I tried it with Petrie and Timms and the maps show that all the Petries (Dad's side) were in Scotland in 1881 then drifted down to the middle of England over the next 100 years, and all the Timms (Mum's side) were in London and drifted up over 100 years. This makes sense because if they hadn't, I wouldn't exist.
(I wanted to display the actual maps but I don't have the technological skills to do it. Any computer boffin out there who can enlighten me?)