If it is your debt, and it was opened on 1.2.01 then it is not statute barred. At this stage, if you are not convinced it is yours, you must ask for written evidence to prove it is yours and refuse to pay them anything or give them any details of your finances until they provide it. Get their address and write to them (recorded delivery) asking to be told who the creditor is (name & address) that they are acting for and the account no. of the alleged debt.
They will probably not give you proof it is your debt so,
when you have the creditor's details and if it appears that the debt is one under the Consumer Credit Act, go here:
http://www.debthelpuk.co.uk/cgi-bin/yabb/YaBB. cgi?board=On_Topic;action=display;num=11321687 59
About halfway down the page is a draft letter from "Skiannach" which you have to send to the creditor (recorded delivery). Add to the draft a sentence saying that the payment you are sending (the �1) is not a payment on the alleged debt, but purely the statutory payment for the information you are requesting.
If it is a CCA debt and they do not provide the information then they cannot enforce the debt.
Throughout, keep a copy of your letters & a note of any phone calls (name of caller, date, time & a summary of what was said).