As an author with an interest in place names it is often interesting to see the differences in pronunciation - a good example was Shrewsbury, discussed in my blog of November 2009. There are many other place names which are mispronounced ostensibly because, as with Shropshire's county town, the name was created at a time when the vast majority of the population were illiterate and the English dictionary did not yet exist. Hence those few individuals who could read and write were free to spell however they saw fit and not until the population were literate was the name read by those who had never heard it said (or who did not recognise the name) and therefore mispronounced. (Note these are examples of accepted pronunciation and nothing to do with local pronunciation or regional accents, which is an entirely different subject.)
Among the many (English) place names often mispronounced are:
Beaconsfield in Berkshire - which should be said 'beckon's-field'
Fowey in Somerset - is pronounced 'foy' (as in toy)
Alnwick in Northumberland - should be said as 'annick'
Alrewas in Staffordshire - should be 'allrus' (rhymes with walrus)
Tonbridge in Kent, Honiton in Devon, and Romsey in Hampshire - Tunbridge, Huniton, Rumsey
Derby and Derbyshire - it is 'darby'
Berkshire - is 'barkshire'
Towcester - is 'toaster'
Wymondham - 'windum'
Iwerne Minster and Iwerne Courtney - the basic name is said as 'yew earn'.
Todmorden - 'tod-muh-dun'
Mousehole - 'mow (as in how) zel'
Belvoir - 'beaver'
Leominster - 'lem-ster'
As I have stated several times, place names are rarely created by the occupants but by the neighbours - most are simply descriptions of the place. To those who live there it is simply 'home'. A couple of years ago I spoke on the subject of place name origins in the village of Parwich in Derbyshire. Not wishing to mispronounce the name and upset the locals before I'd even started I asked the audience how they pronounced it. While many outside Parwich pronounce it as 'pah-rich', those present responded with both 'pah - wich' and 'porrich'. This immediately brought some surprised looks and was something I found most interesting for it shows how the residents never used the name of the place when speaking to one another.