side return extension without knocking through

Side Return Kitchen Extension Cost in London: 2026 Guide In 2026, a side return kitchen extension in London (typically 10 to 15m2) costs between £55,000 and £120,000 or more for a mid- to high-specification build, averaging around £3,500 to £5,500 per m2 for construction alone. Bespoke, high-end designs can exceed £140,000. The final figure depends…