This site might be of interest to anyone who's either British or has British ancestry. It can tell you how many other people share your surname - and more interestingly, whereabouts in the country they come from. The site also has data from both 1998 and 1881, so you can see how the distribution has changed over the intervening century.
In my case, there are only 1,436 people in the whole country sharing the same name as me. No, I don't know all of them - but given how tightly clustered the distribution is, I do think there's a fair chance that we're all related. Descriptive surnames like 'Smith' or 'Green' might be arrived at independently by different families all over the country, but such a concentraton suggests a single point of origin to me.
The map on the left (or the top if you don't have a widescreen monitor) is the distribution today, on the right/below 130 years ago. The small yellow dots mark where I was born and where I live now. ;-)
So where does your surname come from?
ETA: Having investigated a little further, the data on 'Frequency' comes from the electoral register. I assume that means the figure is the number of adults with that surname, and ignores people under 18 (and also criminals, lunatics and the Queen). Also, the data on 'ethnicity' simply means the ethnicity of the person's first name.