If it's a bank personal guarantee then rest assured that they will have written it in such a way that you will still be bound by it…
As an example, the guarantee that I have here from Barclays (from 2001) states that:
"You will continue to be bound by this Guarantee regardless of any changes in the amount or nature of the Customer Liabilities, your death or mental illness, or any other matter".
It does, however, also have a clause that:
"You may stop this Guarantee from continuing, and fix the amount you are liable to pay under it, by giving us three months' notice in writing. If you give this notice, the total amount you are liable to pay will be all Customer Liabilities existing at the end of the Notice Period".
Do you have a copy of the guarantee that you signed?
EDIT: Too late, yours is with a supplier… Still, worth checking to see if there's a similar release mechanism that you can exercise.