The swap that looks close
a larger single wall box is the usual substitute for double wall boxes, and it is the wrong one. A larger single wall carton adds air and still has the lighter board.
Packaging Boxes lists Double wall boxes separately because the jobs diverge as soon as the goods are on the bench.
What the right line actually does
Double wall is the stronger board, made in the UK, for heavy, fragile or stacked goods.
The range is also the removal board. It is listed apart from single wall.
If you have already mixed them
Using double wall for everything empties the strong board and hides which line needed it.
TradePro at Packaging Boxes, for trade businesses, starts at 5% off and goes up to 10% when you spend over £1,000 a month, and it adds BACS. It does not change which Double wall boxes you needed.
Open Double wall boxes when you already know this line. The bundle quantity is on the page. Packaging Boxes will still dispatch an order placed by 3pm on the same day.