I've looked on ebay for FFIX and in Australia it is not cheap. All of the listings are at least $50. I've seen ones up for $80-$100.

And yes, the UK does use PAL (my copy of X is from the UK).

I looked on ebay.co.uk and the copies of FFIX are significantly cheaper than the Australian ones, so you probably would be well off just buying a new copy of the game unless you have a friend with a disc 3 to lend you.