I plan to have a macro that gets excel and text files from the web (an
FTP site), saves these file in the user's PC temporarily (for no more
than an hour generally) during which time the user can modify the data
in these files (via a VBA-type interface). When editing is finished,
the macro will put the files back in the FTP site and delete the
temporary copies in the user's PC.

Is the user's C:\ folder (i.e. the root directory) a good location to
store the temporary files? What other folders could be used?

Also is this method of updating files in an FTP site sensible? Is
there a better way?