Sorry but I'm not sure what you mean?
Are you asking if you are liable to pay?
Ok. So what is your question about this?
To achieve what?
Is he a sole trader or a limited company?
Do you have his address? Don't give it to me but do you have it?
Do you have any means of finding it?
That is going to be a problem.
To sue you will need his address. There is no other way of doing it.
Ultimately he cannot be forced to return and put this right if he is refusing. All you can do is sue for the cost of the work if he does not.
You can track him down by using a tracing agent if you have fairly limited information upon him. That is usually under £100 but you cannot reclaim that sum.
If you can get his address then you can issue at the small claims court. It will be cheap and quick to do so.
Can I clarify anything for you?
There are no magic wands I'm afraid.
The only two route are that he gives it to you or you secure it either through your own research or use of a tracing agent.