When buying new windows, does the final payment have to be made immediately on completion?
Buying windows is no different to buying any other goods or services. You and the seller can agree to any payment terms you choose. From the point of view of good customer service I would suggest that you should not be required to pay anything until the goods and provided and (as in this case) any fitting is complete. It is far easier for a business to acquire the goods before payment, than it is for you to be without the money and the goods. Any business that cannot cope with this is probably not financially stable enough to deal with anyway. At the very least I would expect only a nominal deposit to be paid up front. Anything you do pay up front should be paid via credit card, as this gives you a right to claim against the credit card provider if the goods a faulty or not delivered at all. However you pay, you have a legal right to goods that are as described, free from defects, and fit for purpose. If you can prove the defect was inherent in the goods when bought, you can sue for th
