My pet peeve is Ibiza, pronounced as "eye-beetha" by the people who continue to bugger it up as a holiday resort, instead of "ee-beetha" as it should be.

A somewhat more upmarket one is that the "t" in Moet (of "et Chandon" fame) should not be silent - even though everyone seems to want to say "Mow - ay". The Moet family are not French, hence the "t" is pronounced.

See also Nigel's comment about the dreaded term "one pence piece" which saved me a lot of typing.

cheers, Terry