Various rattles and how to combat them?

Hello again everyone. As you might know, I'm a fussy begger when it comes to rattles and squeaks that are found on my Fabia, and I've had a fair few over the last nine months of ownership. 

Now that the awfully whiny gearbox and 'singing' thrust bearing have been sorted, my ear has been drawn to a few new ones. 

The first noise is caused, when pulling away at low speed, by (from what I can figure out) by my grille rattling against the edge of the bonnet - when I plasti-koted my grille, I broke a few clips off it. Is there anything I could use to 'lock' it into place and stop the looseness? (such as tape, or jamming some plastic in it?) 

The other is caused by my number plate surround tapping the boot, that I hastily installed due to breaking my old number plate and having nothing to reference the holes with. 

How hard would it be to drill my new pressed plate without the old one? And is it a good idea to use sticky pads, if I can't drill the plate? Do they invite rust? Would the old screw holes leak or rust, if they have nothing in them? 

Many thanks in advance ;-)