Overpayment From Old Employer

A question about : Overpayment From Old Employer

Hi, I hope someone can give me some advice.
I used to work for a company, and towards the end of my employ there were some issues regarding my pay. Due to an on-going health problem, I was off work a lot and ended up in hospital having a major operation.
During this time, even though I had provided details of absences and doctors notes to HR/Payroll, they still managed to make several mistakes over the course of a few months, overpaying and underpaying me, and generally being a bit rubbish.
When I left, which was in May/June 2009, I understood that it was all sorted. Basically, they kept my final months pay, and a bonus that I was due to receive. The last email I have from them states that as they had not finalised the bonus amount, they would contact me if there was anything else due/any money left over for me.
So....that was 3 1/2 years ago, and I didn't hear a single word from them. I, and I think it's reasonable, assumed it was all fine and settled. I went travelling (but I had left them a contact address that has not changed for the last 10 years) and started university. I graduated in July, and am now studying for an MA.
Out of the blue, I received a letter from a solicitors firm called Clarke Willmott stating that I owed the company Ј269.28 in overpaid wages.
As a full time student I live on a little under Ј50 a week, so that amounts to more than a whole months worth of money for me. I have contacted the solicitors, and told them I need more information from the old employer, and they have have agreed to put it on hold until after the New Year.
Now, the question I have is, will I have to pay this money? I thought that I had paid back everything I was over paid, and have not had any contact from them since the above in June 2009. My circumstances now mean I basically have very low income from a part-time job, and was completely unaware that this money was outstanding. I read somewhere that if you reasonably thought the payment was correct, and that the company have not made reasonable attempts to get the money, and that your current circumstances mean you no longer have the money, you may have grounds for getting it written off. Is this correct?
I am contacting the company tomorrow to try and get the full details from them, but any help or advice would be greatly appreciated.

Best answers:

• If they can prove that you owe the money, you are liable to make payment. You should be able to pay in instalments.
• The key word is prove, absolute and undeniable proof.
  Plus have they sent you any kind of invoice or demand ?
  Or just a nasty letter.
• Thank you so much, I have spoken to the solicitors and the case is on hold til after the new year. I will request all the records from the company and make an appointment with my local CAB. Thanks again.