Are you sure that 1/3rd will cover replacing the 'silly' windows? Have you actually had an alternative quote to replace all the windows that need replacing? If so, does that come to 1/3rd of the total price? You need to be 'straight' here, regardless of how inadequate the company is being. For instance, if what you need and insist on is to have all the 'stupid' windows replaced, then you need to hold back just what it'll take to have that done by another company. If, on the other hand, you can live with these silly windows provided they compensate you to some degree, then that sum should be less than the cost of replacing them - it should be a compromise. What I hope you won't do is hold back the full amount to replace these windows and then keep them without being replaced. That would be unfair, and you'd be no better than this company. I think it would also leave you vulnerable to being sued by them - and rightly so. So I hope you are absolutely clear and fair in what you are saying to them. If so, their choice is simple - agree to sort out "items 1 to 6" as outlined in your letter, or else accept the 2/3rds payment as full and final settlement. (Er, you do have all this in writing, don't you - a list of everything that must be put right before final payment? So that all you need to do is refer to a 'list' and not have to go through it all again...) You are not quite back to square one - you hopefully have all this recorded in detail. So you need to reply - in writing - that you will only provide full payment when all the issues you have complained about have been put right - you have no interest in them coming it to sort a few minor issues, and you will not provide part-payments for such small issues. Add that they have the option to accept the 2/3rds payment as full and final payment and not carry out any more work on your house. Give them a week to reply.