Kostis,

The LEN and CODE functions return the same data for both the range
filled with formulas and the "pure values" range. Since posting, I have
continued to develop the spreadsheet (primarily defining a lot more
named ranges elsewhere) and now the other Array Formulas that I use
(the ones that create the inital two Unique ranges on which the final
array formula is supposed to work) have started giving the same
symptoms. I now suspect that this is not a formula problem, but an
Excel problem - possibly related to the number of named ranges I have
in the sheet, and for some reason the Array Formulas are failing due to
what appears to be something entirely unrelated (I'm using Excel 2003
under Win XP SP2). I sincerely hope I'm wrong and that the problem is
down to ME doing something wrong, but as I see it at the moment,
something very weird is going on here.

Regards,

Huw.