Always fit new head bolts when renewing head gasket. Some Land Rover workshop manuals state that they can be re-used up to 5 times, this is incorrect. The 300tdi Engine Manual (LRL0070, LRL0003, LRL0081, Book ISBN 1-855-20521-1, Page 18, instruction No.4) states:  "Using sequence shown, progressively slacken then remove and discard 18 bolts securing cylinder head". They are torque to yield "stretch" bolts that cannot and should not be re-used.