In reply to henwardian:
A typical scenario for collecting small debts is often along the lines of:
1. They write nasty threatening letters about bailiffs etc.
2. They pass the debt to debt collectors who write more nasty letters
3. The pass the debt to another debt collector who write more nasty letters
4. They might, but not always, call round your house to persuade you to pay (don't answer to strangers).
5. They lose interest, writing occasional nasty letter
6. They try to offer you a deal: e.g. pay off just half the amount by such and such a dateto clear the whole debt
7. They give up on you as a lost cause
If you're NFA I'd say you've got nothing to worry about. They can't even write to you.