G day my Australian friend, I lived in oz for 4 years and was Mini Australia best customer ( i had 5 in 18 months) for a while. In fact the mini salesman in Sydney ( Shaw Harrison) and I are still great friends. he now lives in Brisbane.
K & N and Forge motorsport had my car at their HQ's and did many airflow/ temp and intercooler tests. They said the intercooler is big enough its just that the bits in front are a ' little' obstructive. As for water spray it really isnt needed but will look amusing...I've got both bits that mini mania supply but i didnt get it from them , one is a air divert shovel looking thing with water jets that goes under the front intercooler, the other is the turbo muffler bypass baby bazooka tube. I've also got the blow off valve. none are yet fitted. I've got rolling road reports for the air intake ( + 5hp) and the exhaust ( incredibly + 22 HP)