Thanks everyone for this. I had this problem a couple of months ago - local (non-Ford) garage sorted it for £25.00. But it happened again yesterday. The garage was shut, and I need to get to Norfolk on Tuesday. Poking about in the aperture where you can see the spring sorted it, but the information system is stubbornly showing the bonnet as open - maybe a dirty contact, so I'll give everything a good spray with WD-40 to see if that helps. I've muted the audible alarm, and done a quick drive round the block - no rattling so I'm sure the bonnet has locked.