Ok - then it should not be an issue for you. There is no liability.
It would be for the customers to enforce the contract on the new owner. As a Ltd company you have no liability personally.
But they would, as customers, be able to sue the new owner for breach of contract.
The only other way you could do this would be to seek an injunction to get him to comply with the terms of the agreement.
For this you would need to issue a claim form N208:
The Court would set the matter down and decide whether to compel him to comply with the contract.
However the issue fee for this alone, without legal fees is £355 and hearing fee of £1090
Can I clarify anything for you about this today please?