Ignition key not turning enough to engage the starter Options

[moggy]

I recently had a problem where the car would not start. I isolated it to the starter switch which as when I shorted the relevant wires out at the starter switch the starter would engage and the car swould start. I've now replaced that electrical part at the end of the starter switch mechanism but it has made no difference. If I take the electrical bit out and start it with a screwdriver it starts no problem. It appears that the key does not turn enough to engage the starter. Has anyone else come across this? I can't see anyway to take the tumbler and whole mechanism apart, so am I screwed??? do I have to buy the whole switch/lock/tumbler mechanism or am I barking up the worng tree (IMG:style_emoticons/default/sad.gif)