The pilot reported that as he entered the circuit area light rain was falling, associated with a light and variable wind from the southeast. He carried out a right circuit for a landing approach to runway 07, reducing speed to about 90 kts as the aircraft passed over the threshold. However, the aircraft floated before touching down about a quarter distance along the strip. The brakes were applied but were ineffective in slowing the aircraft. Concerned that he would overrun the strip and the highway beyond, the pilot deliberately groundlooped the aircraft to the right. The left main and nose landing gears collapsed during the turn, before the aircraft came to rest against the perimeter fence. The pilot subsequently learned that it had rained heavily prior to his arrival and thought his aircraft may have aquaplaned on the wet runway surface.