They were awake when the fire started.
It was caused by the dog knocking over an oil burning cook stove, either the stove fuel, or the cooking oil in the pan ignited and the fire spread rapidly in the dry wooden suroundings.
Had they been sleeping it is unlikely that they would have woken in time, though OTOH the stove would not have been lit whilst sleeping, and the dog would have been outside.

In retrospect, the stove should have been fixed down, or even better used outside.
The only lighting was from a 12 volt flourescent light screwed to the wall above the stove, it failed in seconds, presumably the heat broke the glass.

The financial loss was not that great,perhaps a few hundred pounds, but the potential risk to life was great.
They will be a lot more cautious in future.

The dog burnt its front paws, ears, and nose, though not seriously and is expected to make a full recovery.
The owner suffered from minor burns, bruises and small cuts, and has recovered.