The pilot with considerable rotary wing but limited fixed wing experience, was conducting a flight to an airstrip which he had previously inspected by motor vehicle. The airstrip is aligned 080 degrees magnetic, approximately 870 metres long, and is located on the northern side of a tree enclosed paddock. On arrival, and without further assessment of the airstrip characteristics, the pilot joined the circuit for a landing to the east into a slight headwind. During final approach he lined-up to the right of the airstrip until alerted by the front seat passenger. The pilot then realigned the aircraft with the actual strip while continuing the approach. Despite being high he did not consider going around. Crossing the threshold the pilot estimated his height as 50 feet above ground level with an airspeed of 90 knots. The aircraft bounced on initial landing and did not settle until almost 400 metres beyond the threshold. During the landing roll and with only 250 metres remaining, the pilot considered, but then disregarded going around. He applied heavy braking causing the main wheels to lock-up. The aircraft skidded and overran the strip before entering a three metre wide track of soft soil, with a slight rise of firm ground on the far side, which partially dislodged the landing gear. It then continued for a further nine metres before coming to rest ten metres to the right of the airstrip centreline, on a heading of 115 degrees magnetic. The aircraft Flight Manual landing weight chart indicates that the airstrip length was adequate.