I belive I owe this forum an update and a big thank you, especially to Herbie.
I only just had an RX 450h SEL 2009 for a few weeks when the problem started. The symptoms is the Check Hybrid System orange triangle usually shows up. Few minutes after I turn on the heater or the air conditioning, the Check PCS warning light comes on as well. The air conditioning was just cool, never cold. Every few days the car will refuse to start until I get a mechanic to clear the warning lights. The Check PCS light do go off when the car is turned off and switch on again.
I took it to Lexus for a proper diagnosis and they said I need to change the air conditioning compressor. That it seems when the car was regassed the wrong oil was used. They quoted my £3k for parts and labour.
I got a used compressor from Ebay for £185 and my mechanic fixed it including regasing for £300. Now the air conditioning is ice cold. No more check hybrid warning light. No more check pcs warning light. Thank God.
Interestingly when I took it to lexus, the engineer was almost swearing that my car has no PCS. I explained to him the the check pcs warning light do come on and even showed him a small PCS BUTTON hidden above the accelerator pedal. But he insist a 2009 third generation RX does not have it.