I went to an Officeworks today and as per the prices quoted by kovert the other day from their website, it will cost me $100.50 for the three to be done at A1 in glossy poster format.
I have to wait until Friday to pick them up though, so a bit of a wait.
The guy at the register who created the job and took my money didn't question the source of the images to reject it, but I'll have to see if I get notified during the week to say that it can't be done (by whomever actually does the printing).
The $33.50 gloss option is the one that looked to be most poster like, as the $20 option is very flat, like printing the image yourself at home on your printer... while the satin option gives a grainy photograph appearance to the image.
If you can't get it done where you live, see if you have any relatives or friends near one to get it done for you, or if you are willing to pay postage maybe pay someone here to get it done for you and post it.