The kit we found is from Scandia Hus - the Malthouse Barn https://www.scandia-hus.co.uk/designs/malthouse-barn/
They charge nearly 200k for the kit and erection with window installation. They estimate it would cost around 350k for the finished house.
"The building set includes the timber frame with a fully boarded roof, insulation, 15mm plasterboard, plasterboard screws, Swedish triple glazed windows and external doors. Also included are Swedish internal doors, skirting boards, coving, architrave, insulated loft hatch and ladder, open or closed treat staircase and mechanical ventilation system. The estimate assumes standard foundation requirements and a good, above average specification of finishing materials. It does not include any external works, connecting to utilities or associated professional fees."