Apologies for not answering to a previous question or two in this thread - I've only just noticed them (email inbox too full).

I purchased a 16Gb black iPhone from a chain called All Phones in Gateway Shopping Centre, Success (a suburb of Perth, Australia). Despite ringing a bunch of stores, I couldn't find a prepaid version anywhere - all sold out - however this store had the phone I wanted, so I bought on a 12-month contract for AUD $960. You then ring Optus to request unlocking, which apparently takes 10 days. no additional cost.

I get to Dubai on 21 August, so we'll see what happens when I try it on the Etisalat network.

Cheers, Steven