The pilot reported he had completed five touch-and-go landings, and two glide approach landings on runway 16 during a session of circuits, the latter requiring very close approaches. The wind was from the south-west at 10-15 knots, resulting in a gusting, right crosswind. The accident occurred while the pilot was carrying out a third glide approach. He advised that he would normally extend the undercarriage on downwind leg as the first of the vital pre-landing actions, and on final approach do a last "three greens" verification check. On this occasion he did neither check, being busy with the wind gusts and the very brief base and final legs. The aircraft touched down smoothly and slid for about 70 metres, coming to rest on the centreline. It was then that the pilot heard the undercarriage warning horn and saw the undercarriage control in the gear up position. He turned off all switches and evacuated the aircraft. The pilot said that he had been suffering the after-effects of a head cold and this, together with over an hour of crosswind circuits, may have reduced his sharpness to the stage where vital actions were forgotten.