Sorry.

There are 5 of us travelling and we've paid for 3 bags at 20kgs each.

Bags 1 and 2 are well under according to my bathroom scales. Bag 3 is just under, but those scales aren't always the most accurate. My concern is that the airport weigh it as 21kgs so even though we're totalling well under 60kgs, they get anal about the one bags that's just over