Crystalate Holdings Plc is warning shareholders to expect very disappointing first half profits for the six months to March 31 after problems at its Welwyn components and contract assembly division: the micro-circuits division has run into trouble on a key product, and its circuit board unit is performing poorly; Lord Jenkin, former Tory minister Patrick Jenkin, is to become chairman of Crystalate, succeeding Nigel McLean, who resigned after reported disagreements over other management appointments.