Statute of Limitations applies in this case because it's such an old debt. This means that Littlewoods can, and have, passed your debt to a debt collector, who are legally within their right to chase you for the money but they cannot (I believe) threaten you with court/arresting your wage etc.
If you have moved home or anything in the last few years and simply not told Littlewoods this, then they can claim that the statute is null and void and further action will eventually be taken.
For such a small sum of money, can you not just agree a monthly payment plan with the debt collector?