How to terminate a builders contract?

[EB48]

We have a JCT minor works contract with our builder, where we retained 5% of our payment for 3 months. After 4 months, there are still unfinished tasks but my builder has not responded to my requests for repairs and finishing tasks in the past 2 months. At the same time he continues to ask me for his final payment.
I'm planning to write to him to terminate the contract and find other builders to come in and make repairs. I'm unsure of how best to approach this. Has anyone had a similar experience?

What does the contract say. I know in the JCT contracts we sign as subbies there are clauses about making good(snagging) and resolution of disputes.

I have to admit I haven’t come across one being used by a domestic client, only via a main contractor or QS.

It will tell you in the contract what to do. Do you have a contract administrator, if so they should advise you? If not, the the MW contract was not suitable. If you have legal cover on your household insurance, give them a call.

Do you have a contract administrator, if so they should advise you? If not, the the MW contract was not suitable.

Yes, this. I’d have thought it should have been the JCT Homeowner contract.

Correction it is indeed a JCT 'Building Contract for a home owner who has not appointed a consultant to oversee the work'. Section 2 part 8 says that the customer can terminate a contract after giving 7 days written notice, if the contractor is not at the premises to carry out the work or being negligent in terms of H&S or carelessness. I would then pay any difference to the builder after all the work has been finished by someone else.
My question is really to find out how to approach this problem without getting into a formal dispute situation. I'm grateful for having a contract, but I'm wary of using it if there is not a more straightforward way to handle this problem. I hope this clarifies and thank you for all your replies.