TBH I would call him and give him reasonable opportunity to finish the rest of the job in one go, to your satisfaction.
Otherwise I wouldn't pay him anything. Half a job is no good to you because as you say, other painters will be reluctant to take it on. You agreed a price for the whole job, not a day rate so you would be within your rights to pay nothing.
He is taking the P billing you for £500
Otherwise I wouldn't pay him anything. Half a job is no good to you because as you say, other painters will be reluctant to take it on. You agreed a price for the whole job, not a day rate so you would be within your rights to pay nothing.
He is taking the P billing you for £500