Why UK fitters usually quote 10% waste, not less
Most UK flooring retailers (Wickes, B&Q, Tile Giant) print a "coverage per pack" figure on the box, but that assumes zero waste. In practice, laying laminate or engineered wood in a standard rectangular room needs about 10% extra for end cuts, and a diagonal layout or a room with several alcoves and chimney breasts (very common in older British houses) can easily need 15-20% extra.
Underfloor heating and expansion gaps
UK building regulations do not fix a legal minimum expansion gap, but manufacturers typically specify 10-15 mm around the perimeter of a floating floor to allow for thermal movement, particularly important with underfloor heating, which is increasingly common in new-build extensions and kitchen renovations. This gap is covered by skirting or a scotia trim, not deducted from the area you need to order.