The key thing we need to learn in the AAIB report is what exactly the Fire & Rescue Service informed the crew when they inspected the aircraft with the thermal imaging camera.
The way I was taught (from Airbus) cargo smoke warning:-
ECAM leading to LAND ASAP.
Bring the aircraft to a stop on the runway, cabin crew members to be on station.
Fire service to inspect the aircraft with thermal imaging camera, not to open the holds.
In the event of nothing showing via the camera - consider the passengers being removed from the aircraft via steps.
If the aircraft is showing signs of heat from the hold then evacuate the aircraft - once passengers are off fire service open the hold.