A practical 2026 pricing guide for homeowners in Worthing and West Sussex. Single-storey extensions typically land between £2,200 and £3,000 per m², double-storey extensions offer better value per pound and wrap-around extensions sit at the top of the range. This article breaks down what drives the price — groundworks, glazing, kitchens, roof type, finishes and site access — so you can budget realistically before requesting quotes.