Please convince me I'm not being unreasonable - builder invoices

[MummytoMog]

Our builder wants us to pay the completion invoice on our loft conversion - backstory is that we've only contracted them to do it up to first fix and there's a fairly detailed quote behind that.

Some stuff doesn't make sense to do now, because the new side extension will cut across where they would otherwise tile the side of the dormer, and where the new gable end wall would be rendered. Then there's a couple of bits on the quote which would normally not happen now (balustrades on the stairs, fixing the ceilings on the first floor) but during second fix and plastering. I am happy to wait for those to be done, and even happy to pay the completion invoice on the basis that they will be here doing the extension and I will have a hold on them that way.

I've asked for list of the things which are not yet done, but have been paid for, before I pay the invoice. I got a pretty snippy response back saying aside from the tiling it was all done. So I sent back a polite annotated copy of the quote, with a list of what I thought still needed doing. No response yet, but I'm feeling really anxious and like I'm being unreasonable. But I just want everything to be clear so we're not in dispute further down the line? I'm perfectly happy to pay the invoice, the minute we have agreed on what is left to do.

Pah. This is why people pay project managers right?

perfectly reasonable.
nail them to the floor line by line about what you are paying for if it has deviated from the quoted work in any way

Maybe I don't understand but why pay for work they've not done yet? Do they need a deposit and is it clearly stated as such? Otherwise, I'd pay for what they've done (ie first fix) and pay the rest when they come back and complete it. Particularly if they're claiming all work bar tiling has been done when you know otherwise, I'd choose not to trust them with money which they are actually yet to earn. I don't think good builders are also always good with paperwork and an arguement weeks or months down the line about what this payment covers would be annoying if it could be avoided now.

Well I haven't heard anything over the weekend (didn't really expect to, I don't work over the weekend so I don't think that he has to). The completion invoice only covers to first fix, and we will renegotiate second fix and plastering when we are at the same stage in our extension (the hope being that it will be cheaper to do it then). But there are a few things on the quote which are slightly unusual (we wanted a floor down so we could store stuff during the extension build, we had a boiler moved, the staircase should be finished so we can use it) which haven't been done. I think this is because he has slightly struggled to keep the unusual aspects of the quote in mind, so incompetence rather than malice, but as you say, I really do want it sorted now. Although in the end I did actually pay the invoice, as I suspect the on site builders wouldn't have been paid if I hadn't. But I have plenty of hold over them at the moment, so will just have to keep banging on about this now.