Just had a debt collection letter saying a warrant is being issued for a £513 I knew nothing about... What do I do?

I'm not sure what to do about this, or where to get help.

I have received a letter this morning stating that I have an outstanding penalty charge notice from the 14th September 2016, and the amount owed is now £513.

Aparrently previous notices had gone to my last address, rather than my new address. The letter states "a warrant has been issued authorising us to remove goods at the previous address", and "an application has now been made for the warrant to be re-issued for the new address."

The penalty charge is due to me driving in a restricted area.

I do not dispute the initial penalty notice, but this is the first time I have heard about the fine, can i be expected to pay the full amount, and should I be expecting bailfs at my door?

The fine is from 14th September. I moved home in the middle of August, but i did update my address with the DVLA on the 24th of August, so I'm not sure why I would not have received the letter.

This is the only mitigating circumstance that I have...but i think i'm justified in saying I should not pay the full amount.

Can anyone help me figure out what I should do now?