I wonder if there could have been some form of half way house here. Would it be possible say for the MoD to have said, "Please donate to fund X, and we shall distibute all the cash to charity", at the same time publishing a list of who gave what and where it went, which would still show the troops that there is a supporting public back home.Or how about using the e-bluey system for christmas cards to "A soldier/ airman/ sailor" as we print those off in theatre so they're not actually carried anywhere.
Completely agree that mail from one's family should get priority but in an age when people in theatre question whether or not they're valued by 'the man on the street' it seems a shame to turn off a public demonstration of support with only a glib alternative offered in return.