Yes – and many of our customers do!
In fact, a lot of people say that this is one of the best, most attractive and most practical features of their new kitchen, especially when the windowsill is “fully sealed” with an upstand completely filling the gap underneath it down to the worktop. This allows for cleaning/wiping down (which may be frequent if you have herbs or other pot plants on the sill) to be easily done with no smears onto paint work, and with the same cleaning treatment on all horizontal surfaces.
An installation showing the use of an upstands and a window sill. In this case the height of the window sill has been met by increasing the upstand underneath to give it that perfect finished look.
Above you see the white upstands then meeting the window sill and on the high unit we have gone into the window recess to give it that seamless look.
As you can see the worktop, upstand and window sill all meeting. This gives a finished look and helps with the ease of cleaning.