Giro have a crash replacement policy where you send the helmet to the UK distributor with a fee(much smaller than a new helmet) to cover a replacement.
Although you haven't crash damaged yours I'd give them a call and see what they say as it shouldn't have developed cracks on its tod and they can probably run some tests, trouble is if they say you may not have looked after it and received a knock somewhere I don't know how you'd go about proving otherwise . Do a forum search as I put the details up in a post somewhere a while ago when someone else was after the contact.
It might have to wait until you are back though or the phone and postage cost would probably be prohibitive back to the UK (you'll also need the receipt). Might be better trying to pick up a cheap titfer over there to see you through the next couple of months and then have it as a spare when you get back.