UK prius - No low tyre pressure warning!

Had a completely flat rear tyre couple of days ago - Unfortunately I only realised after a cyclist knocked on my window and kindly told me while stopped at the lights!

I have since had to replace the tyre as there was a large screw lodged in the inside tyre wall and so puncture repare wan't an option.

Anyway, I was pretty sure the prius had the low pressure warning system and so after reading around pc I came to the conclusion that maybe the system needed to be reset by pressing the button (i've only had the car for a month) - but low and behold, after finally managing to bend my head upside down with a torch light in one hand and look under the steering wheel for the button, it wasn't there, instead there is just a black plastic stopper thing. I was NOT impressed.

Does it really not have the low pressure sensor system?

I'm pretty sure there is an orange ((!)) light on my dash which does light up with all the other lights when the car is first switched on.

Any fellow UK members had this issue? or am I missing something here?

2007 T-spirit.