cheers, guys, velocity, that does sound like it could be what is happeneing,

ive also been thinking... on saturday morning, it was nice and warm and the sun had been on the garage door all morning making the inside of the garage hot and also the back of the car where the petrol tank is. Say for example if the carbon canister solenoid had failed and stuck open( the one bolted ot the inner wing near the fuel pipe connectors in the engione bay, could the heat of the sun make the fuel in the tank warm enough to be purged up the breather pipes from the tank through the failed open solenoid and into the engine breather/inlet manifold pipework - filling the engine with lots of petrol/vapour, and then when the igniton is turned on and the test spark ignites the lot and BANG!!

ill pull the breather pipe off and try it 2nite with the plugs out and the injectors disconnected, to prove there is a spark when its being cranked and that no petrol is coming out of the injectors just due to the pressure in teh fuel rail.