I had thought about trying another key but as I have two which behave exactly the same and one doesn't appear to have any wear I'm not sure that would resolve the problem. Which bit do you mean by the doofer do you mean the actual electrical switch. I've not yet actually taken an ignition switch apart so I'm not familiar with the components used in the complete assembly.
I've had a look on the gpc website and they list a complete lock set for ?50. I've emailed and they confirmed that the set includes the ignition, both doors, tailgate and the glovebox lock. I'm just waiting for confirmation that they are all genuine parts. Seems like a good deal to me, my tailgate lock doesn't currently work so I may just consider changing the whole lot.