Good question Robin:
Italians don't call Florence 'Florence', German's don't know where Cologne is.
French call London 'Londres'
Many places in Belgium have two names
Americans pronounce Leicester as 'Ly-chester'. A few Americans even pronounce Edinburgh as Edinberg
Nobody outside Israel talks about Bet-Lechem and beyond the Arab world it is rarely referred to as Bayt-Lachum. I was quite surprised when it turned out I was in the middle of Bethlehem.
So really it shouldn't matter too much how you pronounce the name of a place. But the closest to 'correct' has to be the local pronunciation.