Need some help please on fixing the bonnet lock of a mini k, it just won't lock down at all and the lever doesn't move freely at all, apart fromm just greasing it up does anyone have an other suggestions.
Should the two plates slide on top of each other or is one meant to be inside the other.

thanks

Check that the latching plate (the one that slides sideways) is free to move without binding on the fixed plate. The round spacers (2 off) should give sufficient clearance for this to happen. The spring should pull the plate across to the locked position without any resistance. If this doesn't happen check for any distortion in the plates and straighten if necessary. I have seen some of these mechanism where you need to add a 1/4 ID washer to the spacers to get enough clearance for the locking plate to slide easily.
Add a slight smear of grease to the slides, make sure that the cone shaped locking pin is aligned vertically over the hole, tighten the lock bolts and all should be good.

good luck.

Also check that the lock-nut on the centre pin hasn't come loose (that greasy springy thing attached to the middle of the bonnet that you keep hitting your head on )

This pin is threaded and can be screwed in or out to adjust how tight the bonnet is held shut at the front. I've had cases where the lock nut has come loose and the pin has screwed itself in enough to be hard to get it to latch into the lock on the slam panel.

Even if the nut isn't loose, maybe someone has adjusted it a bit too tight. Try loosening the lock-nut and screwing the pin out a turn or two and see if that helps it lock easier (don't forget to re-tighten the lock-nut when you're happy with the adjustment )