I see it on the tube map whenever I am in London and it just sounds so posh. The name actually makes me think it should be a champagne brand rather than a town.
The surrounding towns are certainly posh like Chalfont St Giles (Think Noel G used to live there) and house a lot of celebrities, including Ozzy Osbourne at one time.
Most of South Buckinghamshire is pretty wealthy. I wouldn't say The Chalfonts are all that posh... but nearby towns like Gerrards Cross and Beaconsfield have average house prices in excess of £1M.