Some British surnames are not always pronounced as you would expect.  Here are a few examples.
Althorp Awltrup   Hobart Hubbart
Anstruther Anster   Home Hume
Ayscough Askew   Inglis Inguls
Auchinleck Affleck   Jervois Jarvis
Bagshot Bagut   Keighley Keethly
Barugt Barf   Knollys Noles
Beauchamp Beecham   Legh Lee
Beaworthy Bowry ("bow" as in "bow-wow") bɑʊərI  
Bethune Beeton   Leveson-Gower Looson-Gaw
Blyth Bly   Mainwaring Mannering
Bosham Bozum   Marjoribanks Marchbanks
Brougham Broom   Menzies Mingiz
Cadogan CaDUGgan   Pole Pool
Charteris Charters   Pretyman Pruttyman
Cholmondeley Chumley   Rothwell Rowell
Colquhoun Kohoon   Rouse Rooz
Couch Cooch   St. John Sinjun
Cowles Coles   St. Maur Seemore
Cowper Cooper   Strachan Strawn
Crespigny Crepny   Theobald Tibbald
Dalziel Dee-ell   Villiers Villers
Daventry DaIntree   Wemyss Weems
Dealtry Dawltree   Wriothesley Roxley
Derwent Darwent   Yonge Yung
Featherstonehaugh Fanshaw   Youghal Yawl
Foulis Fowls      
A useful source of the pronunciation of surnames (which often match placenames) can be found here.