Dormer loft conversion costs in Worthing & West Sussex for 2026: rear £45–65k, L-shaped & full-width £65–90k. What drives your final price. This guide is written by PG Property Repairs and Renovations, an FMB and TrustMark accredited building company based in Worthing, using real costs and timescales from projects completed across Worthing, Lancing, Shoreham, Brighton and the wider West Sussex area.