I have had my Sony Xperia Z1 compact for 18 months and the battery was running down from 30% to 0% in seconds and then switching off. In addition the power button had got so stuck I had to use the camera button to unlock the phone. After filling in the online form I was sent a box (phambulance, cute) to send my phone back free of charge. Sent last Friday 2nd Sept 2016. On Tuesday 6th September they tried to deliver a brand new replacement hand set, which using DPD's pick up service, I collected last night from my local corner shop.
I had been scanning the forum for reports of what the service standards for repairs were like, and was worried I'd be landed with an "out of warranty" repair bill. I am happy to report that did not happen, and the service I received was excellent.