I have some module 22, 23 and 24 questions knocking about that I can post on to you when I find them. The Pallett book is definately worth investing in, but it has no section on GPWS, but you should be able to get enough gen from a maintenance manual to cover the exam questions.
I might have some old Oxford or Brunell otes about and I could copy the relevant parts - again if I can find them.
The reason for me being so dis-organised is the number of house moves I've had in the last 18 months, but I'm sure they're not too far away. I'll get back to you early next week with news.