I have had two envelopes in the post before - one saying "You are overdue and we will take steps blah blah blah and reposess your house blah blah blah sell you son as a slave sort of thing", then open the second, dated the same day, basically saying "Hi, you owe us £X, can you call and pay it within three months (no interest)?"

I call them and lay into them. Then wait for two and a half months and pay them back. OK, I know I owe money, but if I call up a month earlier and ask to pay and you say not to bother yet... I ain't going to bother until I have to with that treatment. Twice. Damn government company I have to use.