Thanks for all the advice so far. We're new to booking guests and had thought of most things but not this one.

If all those who had bought tickets had turned up then we would have had a full house with more or less exactly the right number. It may have been a question of the forecasted snow, but the band made it and they had a longer journey than any of the absentee ticket buyers.

Maybe thinking of offering a 50% refund or free tickets for the next book guest as a goodwill gesture.