Well, hash in the UK, the pound sign in America.
Unicode has a reference name for every character. In an international
forum, it's surely advisable to lean heavily on an international
notation (which, by the way, is my objection to US-specific date
formats, which are so often misunderstood anywhere else).
http://www.unicode.org/charts/
http://www.unicode.org/charts/PDF/U0000.pdf
http://www.unicode.org/charts/PDF/U0080.pdf
At least in *this* context I'd be confident of readers understanding
what a "hash" is, even though that's not its formal Unicode name.
But given that "pound sign" is the formal name of U+00A3 - the pound
sterling currency sign - it would be a mistake to use that term to
mean anything different.
Many UK keyboards have an actual pound sign in place of
the hash...
You mean US keyboards have an actual hash sign in place of the pound.
Ho hum.
of course most people in the UK have no reason to use the hash key,
On the contrary: it's one of the buttons on a telephone dial pad, and
often needed for instructing users on what to press in such an
everyday context.
But that's OK, I don't even need to hold down the shift key to get one
on the keyboard (it's just to the left of the carriage return key -
same key as the tilde ;-).
Google suggests
http://www.goodtyping.com/teclatUK.htm
............................octothorp, mumble.