All claims about the size, quantity, quality/standards of double-glazing need to be supported by satisfactory evidence.
For claims such as “six double-glazed windows any size from just £X,” all important limitations must either be included or qualified as extra (e.g. number of panes, openers, installation costs, etc.).
“Cash-back” offers may involve a minimum spend and qualifications may be needed as to whether the customer receives the cash outright, whether it forms a deduction off further purchases, or whether the offer is underwritten by a finance company.
Where claims about improved energy efficiency are made, the nature of the comparison must be made clear, e.g. “compared to single-glazed windows, our energy-efficient range can save an average of…”