I'm in the midlands, I took it to the only store nearby. I'm not sure they were allowed to replace the machine, but I was told that because there were no hard drives in stock in the area and it would be more than two weeks for delivery, that they were swapping the machine. I also have Apple Care which probably helped. I also mentioned they had my machine for two weeks six months ago and I couldn't wait that long again for my machine because I run my business off it.
I think they did it because it was the second repair in six months and I asked for every other option to get it fixed faster before they offered me the machine. I also mentioned that the drive I needed would be out of stock before she even tried to order it because there was a problem with the 2012 MBAs. She said there wouldn't be, but I think that also helped. I knew about the fault.
It's really going to depend on the store, who your dealing with and the problems you describe it having before it died on you. I mentioned other minor faults since the logic board had been replaced as well (one USB wouldn't work all the time and I had to keep using my finger to pull the ports back into place to use them). I also told them about how hot the machine had become the night before it failed on me. I did get someone who really wanted to help me and I guess the store manager who authorized it didn't want to deal with an angry customer.