Castle Property Investment Holdings has completed construction of business units at Bryn Cefni Industrial Estate in Llangefni. : Castle Property Investment Holdings has completed construction of business units at Bryn Cefni Industrial Estate in Llangefni North Wales developer Castle Property Investment Holdings has completed construction of business units at Bryn Cefni Industrial Estate in Llangefni. The development known as Llangefni Trade Park, off Industrial Estate Road, has already attracted two pre-lets to Screwfix & ToolStation and completed a letting to Concept Spa Ltd.