Out of date cheque - Money still owing

[featheryfancy]

Hi,
I was wondering if anyone had any experiences or could offer any advice about some difficulties I'm having regarding an out of date cheque.
In 2015 I placed an order for some bedroom furniture paying cash. There were some issues with the order meaning that one of the items had to be changed. The company issued a cheque to me for the difference of roughly £175.
During the move I misplaced the cheque and completely forgot about it
Earlier this year I found the cheque in some paperwork and immediately contacted the store who told me that I would need to contact their accountant who should be able to help me as the cheque was now out of date.
I initially received a response from the accountant saying that they would need to pass it over the another accountant as it's not in the current financial year.
This has now been ongoing for 4 months and the account has ignored all of my emails for the past 2 months.
Does anyone know if there anyway that I can escalate this or pursue a claim against the company as I realise that the fault was originally mine for losing the cheque however they still owe me the money?
Apologies for the long post and thanks to anyone who has read

Take a photocopy of the cheque. A cheque effectively says "yeah, I acknowledge that I owe you the money" so they can't deny the debt if it goes to court.
Then try to bank the cheque. What's the worst that could happen? I have known a cheque to be honoured two years after it was written.
If feeling paranoid: pay it into an account, wait for it to clear and then close that account so that they cannot try to claw it back.

bank the cheque, there's no time limit on them anymore, unless they have cancelled it on their end.

Sorry to drip feed there is slight damage to the cheque where the amount is written, where it says one hundred and seventy five pounds the 5 isn't visible as it had stuck to another piece of paper in the drawer.
The £175.00 in figures is still completely visible however.
Do you think this could be worth attempting to cash?

Thank you both for your replies

It's worth a try - I don't see that you can be any worse off, but do take a copy before it leaves your possession.
Can you still read the missing 'five' from the other side of the cheque?

Banks will ask permission to cash cheques older than six months but they are valid up to six years so it's definitely worth a shot. They may ask you to get it reissued because of age/damage but equally they might handle that bit with the payers bank. It'll just take slightly longer to clear in that case.