John Wells was mentioning (here) the unpredictability of the pronunciation of British place and family names from their spellings, and some are recorded in the Dictionary of Blunders. The fact that they are mentioned at all must mean that in the author’s opinion they were being mispronounced, and this may be giving us an indication that in some cases the pronunciation was actually changing at the time he was writing (the 1870s or early 1880s).
ABERGAVENNY (family name) is pronounced Abergen’-ny. (This is also still, apparently, the pronunciation of the Marquis of Abergavenny, although it is not his family name.)
BELFAST is pronounced Bĕl-făst’, not Bĕl’-fast. (The author does not specify the exact pronunciation of ‘a’ the second time. Nowadays either stress pattern seems to be acceptable, and either /æ/ or /ɑː/ for the ‘a’.)
BERKELEY STREET is pronounced Bark-ley Street, and not as spelled.
BERKSHIRE is pronounced Bark-shire, and not as spelled. (There are some British dialects in which ‘er’ is still pronounced /ɜː/.)
CARSHALTON is pronounced Casehorton. (The BBC Pronouncing Dictionary of British Names acknowledges that this had existed, but by 1971 was no longer heard. The pre-war BBC publication Broadcast English II, which covered English place names, did not include it at all.)
CHOLMONDELEY (family name) is pronounced Chum’ley.
CINQUE (the Cinque Ports) is pronounced like sank. (Not today it isn’t. The BBC recommendation is ‘sink’.)
CIRENCESTER is pronounced Cissester. (Strangely, the BBC’s original recommendation, in 1930, was /ˈsɪsɪtə(r)/. Nowadays, the spelling pronunciation has prevailed: /ˈsaɪrənsestə(r)/, and I believe it is often shortened to /ˈsaɪrən/.)
COCKBURN (family name) should be pronounced Coburn, and not as spelled. (This applies to the port, and some years ago, an advert appeared in the London Underground:
Said King Charles to his court
“I enjoy a good port.”
Said a courtier game
“If I tell you the name
of the best will you make me a knight?”
The king nodded his head
and the courtier said
“Cockburn’s Port is the port for a king.
But remember to say it without the C K.”
So the court cried “Long live Harles the Ing!”)
COLQUHOUN (the name of a person) is pronounced Cǒ-hoo’n. (It still is.)
COWPER. The poet called himself Cooper, and not Cow-per.
CRICHTON is pronounced krī’ton, not krĭk’ton.
HELENA is pronounced Hĕl’-ĕ-na, not Hē-lē’na.
JACQUES is zhāk in French and jakes in English. (This is ambiguous, because the writer uses ā sometimes for /ɑː/ and sometimes for /eɪ/.)
MACLEOD is pronounced mak-loud, not măk-le’-ŏd.
MAINWARING (a family name) is pronounced Mannering.
MARJORIBANKS (a family name) is pronounced Marchbanks.
NAOMI is pronouncec Na’-o-mi, not Na-ō’-mi.
NASMYTH is pronounced Na’smith, not Naz’-mith.
PHŒBE (a female Christian name) is pronounced Fē’-bē.
ST. JOHN (a family name) is pronounced Sin’-jun.
ST. MAUR (Earl) is pronounced Sĕ-maur.