You could try a local repairer (not an electrician) or a national one.
To determine if it can be repaired or not would require an engineer to visit (if you can't diagnose it yourself) and determine the cause.
Click here to find a local repairer (if there is one).
Fill in your details and it will list engineers that repair your appliance.
Alternatively, click here for the current offer from British Gas.
They'll repair the appliance for a fixed price. Put the appliance on a contract and they reduce the price of the repair, normally.
If they can't fix it, there's no charge.
If you want to try repairing it yourself, check the compressor at the bottom rear of the machine to see if it's running.
Check for any ice inside the freezer.
If the compressor is running and there's no ice, it's a system fault and isn't a diy repair.
Hope this helps