Only try this at home
Don't take your key out of the ignition and then drop it down the back of the header tank like i did last night, unless you are at home and have access to a bent wire hanger and a chop stick.
I now have a plastic key fob on the key ring, so in future it won't dissapear down the dark cavernous hole at the back of the header tank.
Doooooohhhhhhhhhhhhhhhhhhhhhhhh.