You're right, bit 7 if the respective IOCON registers were set to '0'. I set this bit to '1' and now these pins works as expected. Thanks!
You can try this:
LPC_GPIO0->DIR = 0x0;<span class="Apple-tab-span" style="white-space: pre;"> </span>//set PORT0 as input
LPC_IOCON->P0_7 = 0xA0;
LPC_IOCON->P0_8 = 0xA0;
LPC_IOCON->P0_9 = 0xA0;
Just force the whole port to input and set the pins to the default state (and making sure bit 7 is set). This worked for me. The PIN register was changing value when I force the pins HIGH and LOW.
This is indeed a specialty of the W type pins.
Have a closer look at the respective IOCON register, with particular attention to bit 7 :-)