Thanks for the input, guys, especially Globaliser for a very full answer. PV, yes we intend to stay in Port Douglas if possible, my SIL went last year and highly recommended it, but I was assuming that we would still have to fly to Cairns.
I have had a quick look at flights, and, as we live near BHX, it looks like it is favourite to fly from there as it doesn't seem any dearer than the London airports. The top choices seem to be Emirates, via Dubai, and KLM, via Amsterdam, change to Malaysia at KL. I've flown KLM often enough before but never Emirates or Malaysia. Any advice on these, anyone?