Yeah, this also happened to me, same exact thing. Went to bed, phone was working. Woke up, phone was off (it had enough battery to survive the night). Wouldn't turn back on, wouldn't react in any way to plugging in to original charger, different chargers, different cables, etc.
I'm in the process of mailing it to fxtec for repair right now.
When emailing support, my experience was it took about 7 days to get a response. You might be able to expedite by sending them pictures with your first email, as they asked me for a total of 10 pictures: top and bottom of each corner, the USB port