I am very surprised you dealt with anyone who just knocked on your door (very dangerous).
I am also surprised you left details of your name and address (and maybe other personal details) in stuff you gave a total stanger.
Have you not heard of identity theft?
Did you not see Fraud Squad last night were the police said peoples names and addresses are "sold on" to criminals and scam artitst so they can buy credit cards and get loans using you personal details, or contact you for all sorts of scams.
You better hope it is JUST a fine from the council and not the worry of baliffs knocking on your door in three months time for defaulting on a loan the scammers took out in your name and you knew nothing about.
NEVER deal with anyone who just knocks on your door.
I am afraid in this day and age you have to be careful of EVERY phone call, EVERY email, and EVERY person who knocks on your door.
Read here about identity theft
http://www.identitytheft.org.uk/default.asp