there are unique headers in the columns, and they (and the data) are
derived from a pivot table in a different worksheet.

(though some of the rows  are hidden as well).

I'm still pondering how best to do this, the process will only need to
be run once a month, over 15 to 20 repititions, so I might settle for
a CPU-intensive solution and run it over a weekend.

Not ideal, but will do as a kludge while I investigate something more
elegant.

I'll post an update once I've decided upon a solution.