As has been said, I would be concerned about any damage caused during it coming down. Granted, I have exactly one case study to refer to (when my roof was done), but I was going purely on the builder coming back to fix the work on his word. Scaffolders smashed up the new fascia and gutters and just fucked off. In future I will be considering "work complete" when all kit and agreed rubbish is removed. 25% is a big whack though. But as has been said, it could still come down within what is a reasonable amount of time to pay the invoice. If it were me, I'd pay it when the scaffold comes down and you're happy there is no damage/everything is done. If that doesn't happen before they chase for payment, just say the work isn't done until everything is cleared. Maybe offer to pay 20% of the remaining 25% (or 80% of the outstanding balance, however you want to look at it) and the rest when the scaffold is removed.
As has been said, I would be concerned about any damage caused during it coming down. Granted, I have exactly one case study to refer to (when my roof was done), but I was going purely on the builder coming back to fix the work on his word. Scaffolders smashed up the new fascia and gutters and just fucked off. In future I will be considering "work complete" when all kit and agreed rubbish is removed. 25% is a big whack though. But as has been said, it could still come down within what is a reasonable amount of time to pay the invoice. If it were me, I'd pay it when the scaffold comes down and you're happy there is no damage/everything is done. If that doesn't happen before they chase for payment, just say the work isn't done until everything is cleared. Maybe offer to pay 20% of the remaining 25% (or 80% of the outstanding balance, however you want to look at it) and the rest when the scaffold is removed.