I am sure the AAIB will be thorough and hopefully prompt on this tragedy.
Have seen a couple of aircraft suffer engine fires (carb area) on the ground at start up and both extinguished promptly with an extinguisher - one a Cessna 182 and one a Rotax 912 homebuilt.
Somewhat worried by reference in a banbi buyers guide to the possibility of leaking fuel tank seams so I am sure the relevant people know about this.
Sad end to fellow fliers.