fire fire help help!

hi all im new here, sorry to start with a question of woe!

ok i have a peugeot 306 miami 1997, with a solid engine 1.4 petrol etc, 120k

i was chatting to my mate the other day, heard a dull bang looked round and saw what i can only describe as a grey beard of smoke emerging from the side shuts of my bonnet, in a rush i popped the bonnet to my horror and discovered the fuel lines on fire!!!

which in turn when i put the fire out is that the wires to the alternator, brake fluid res burned, fuel lines burned and wires to the back of res and the alternator burned. now the mysterious thing is the car had been sitting swithched off for at least 30 mins......yes i know, its odd! chicken and egg! what could have caused the fire??? alternator on fire? fuel lines leaking?....

can anyone help or advise please, i want to replace these parts as the ass's at the insurance gave it a cat b write off..... i can get the spares no problem but could it be a fault further down in the depths anywhere! over to you experts...........