Tony,
I'm just awaiting the arrival of a large lot of Nyassa stamps I bought on
ebay - not sure what's in it, precisely, but I know that from my point of view they're all duplicates, so if there are any that would fill any gaps in your collection I'm sure we could sort something out.
Incidentally, for the sake of completeness, have you had a look at Mozambique's issue from December 1985 on the theme of the Companies of Mozambique - four stamps, two of which feature stamps from Nyassa's 1901 King Carlos issue, and two of which feature stamps from the Mozambique Company's 1918 issue. Google "The Companies of Mozambique" "21 December 1985" and you should find it.
GS
PS - you can tell from my avatar that we have something in common!