Peugeot 307 - Boot won't lock?

Hi all,

I recently bought a 52 plate, 1.6L Petrol, Peugeot 307.

I previously owned the Diesel version and had no problems with it. I ventured for a petrol...

Had it for a few weeks now, and all of a sudden the boot does not lock. When you close the boot, you can hear the mechanism doing something but the boot does not lock and you can still lift it up. It remains unlocked whilst driving. The only way to lock it is to hold it down and lock the whole car remotely.

Any ideas?

Thanks
Iain