Uncharacteristically I had an easy run on this, so much so that this is the first time I've looked at this forum. All this makes me feel I must have missed some sort of point.
So (Malone and other friends):
Having completed the grid I now intend to colour four thematic items in a shade of blue (my father wore this when he was still serving in 1946 when I was born!). I then intend to colour 21 squares that don't overlap with the thematic items in a metallic colour to reflect an abbreviation.
Could someone confirm that I is no more complicated than that before I put on my 39 acrosses and try to get to a postbox.