Range from the cheapest window sill replacement £200 (Blana Floor Sanding based in TW1) to the dearest window sill replacement £1,000 (ThePlumbers.org based in TW7).
Comparing carpenter and joiners estimates for replacing a window sill gives you an idea of who will be better value but the best way to compare costs is to get actual quotes.
What to do - Get rates and quotes to replace a window sill in Kew by posting a job with HaMuch and we will send it to carpenter and joiners in Kew.

"Window sill replacement - first floor window. Also tidy up some sealant around adjacent window. "
SW14