There is no JAA reference for fire extinguishers and the CAA examiners have become so frustrated with appeals that they have issued an unofficial crib sheet. They will make sure the exams, in the UK at least, comply with
this pending an official word from the JAA.
The answer to the 'heavy rain' question is the aircraft should increase its approach speed, because the rain affects the lift by 'deteriorating' the boundary layer and also, although its not stated in the answer, increases the aircraft weight and the drag. This technique is not universally adopted, as noted by the Burger Thing.
After an overweight landing I would check the brake temperatures.