It sounds like it's a judgment mortgage.
You can apply to have it cancelled if no payment or acknowledgement in writing was given for the past 12 years. The normal procedure would be to apply to the PRA, who would consider the application, and serve notice on the company to give them an opportunity to say why it's not statute barred. Since the company is gone, that will be difficult, but if you provide evidence from the Companies Registration Office that the company is dissolved, and the names and address of the liquidator, notice can be served on him/her.
You are invoking the Statute of Limitations, so I'd suggest talking to a solicitor