11 or 12 years ago? And they write to you asking if you ever lived at a particular address? Without having definitive proof that you did so? Did they mention the fact that they were chasing you for a debt?
I wonder how this case fares with regards to the following OFT "unfair practices" listed in their guidelines for debt collection http://www.oft.gov.uk/shared_oft/business_leaflets/consumer_credit/oft664.pdf:
2.2(c) "those contacting debtors not making clear who they are, who they work for, what their role is, what the purpose of the contact is" - did they make it obvious that the purpose of their communication was to determine if you owed money on a debt?
2.8(a) "sending demands for payment to an individual when it is uncertain that they are the debtor in question, for example, threatening debt recovery action to 'the occupier' or sending a payment demand to all people sharing the same name/date of birth as a debtor in the hope that contact with the correct debtor will be made." - do you have any reason to believe that they have contacted you without being certain that you were the debtor in question?
I would recommend keeping an eye on this case with regards to the OFT guidelines - as this is an old debt, then pay close attention to the OFT guidelines relating to "statute barred" debt where no written acknowledgement of the debt or payment by yourself has been made within the last 6 years...
"2.14 In the past we have dealt with a number of statute barred debt cases governed by the Limitation Act 1980, which applies to England and Wales. Based on that experience our position with regard to England and Wales remains:
a. we accept legally the debt exists
b. it is the methods by which the debt is collected that can be unfair as follows:
it is unfair to pursue the debt if the debtor has heard nothing from the creditor during the relevant limitation period
if a creditor has been in regular contact with a debtor before the debt is statute barred, then we do not consider it unfair to continue to attempt to recover the debt
it is unfair to mislead debtors as to their rights and obligations, for example, falsely stating or implying that the debt is still legally recoverable and relying on consumers not knowing the relevant legal provisions, and
continuing to press for payment after a debtor has stated that they will not be paying a debt because it is statute barred could amount to harassment contrary to section 40 (1) of the Administration of Justice Act 1970."