I know I'm a little late but we just had the Glow Plugs replaced under warranty (just) in my partners 2008 model, (I posted in this thread way back).
I left it til very late in the warranty period because i hate the dealership touching our cars, I've found dealerships to be very hit and miss, also i thought the later the better because now the Glow Plugs are new at the end of the warranty period.
Anyway, the problem is solved and we only have to let the "Glow Light" glow once before starting instead of 3 or 4 times beforehand.
I also left it late because I'd diagnosed the problem a while back and knew for sure the problem was the Glow Plugs.
We have 2 diesel i30's and the other one has never had a problem and surprisingly the dealership said they'd never replaced Glow Plugs before.
Bye for now....