not a firefighter, so stand to be corrected, but I have had to attend a number of fires and done some training for them
Their prime responsibility is the preservation of life nowadays so if they, after assessing, the incident feel there is no life at risk (some may think that harsh) they will withdraw for their own safety.
In the TV interviews last night the fire officer acknowledged that the airport equipment had dealt with the "fuel" fire, if you look on the aerial photos on Sky you can see the white of the foam. Most county brigades only carry a very limited amount of foam on their appliances.
Bear in mind that had they been spraying high pressure hoses on the wreckage the damage to any evidence could also have been crucial. Similarly the remains of the house, high pressure could have brought the walls down, possibly on a crucial bit of evidence
The helicopter views also showed a hose on a fixed monitor directed into the wrecked garage where the LPG cylinder probably was (these can take a few hours to cool)