Hiya,
Thanks for getting back to me. I will contact my local Apple store but I live in the UAE and I bought my iPhone 6 at Heathrow at the beginning of April prior to flying out. The only problem I will have is that FaceTime is banned in the UAE, so a replacement won't have it on there and I use this to communicate with my kids back in the UK.
I am trying to charge it at the moment to see if that does anything. I have tried to restore using iTunes but half way through the phone disconnects from iTunes, so that hasn't worked. I have tried the sleep/home button combination and that hasn't worked.
Before I got the temperature warning, my lock screen was saying "slide for emergency" and when I tried to enter my PIN it would just vibrate and not let me in.
I'm gutted as all my IT stuff is Apple and this is the first time I've been let down. Looks like its a trip to the store for a replacement.
Thanks again
Nathan