I was thinking about a badgless grill but seems pricey for what it is. I was thinking alloys. Some nice 15" or 16" but not sure where I would stand with the warrenty as you mentioned
Badgeless grill require cutting the bumper, and I take it your looking at irmscher jobs. You can buy aftermarket grills for like £40-50, but as I say, you have to cut the original grill out.
Alloys, your looking at 17-18" alloys on a Corsa D. Any smaller will look stupid and pointless.
If you out alloys on it, then you'll need to lower it to give it some stance, otherwise your looking at a tractor style.
All of the above will invalidate your warrenty.
I've had a few new corsas, and I didn't do anything to the first 2, then wrote them off. The LE I lowered etc, and just kind of fecked off the warrenty, but only had it 4months from new anyways.
So you have a choice, either modify or keep your warrenty. Bare in mind, D's are expensive to modify compared to alot of cars. So I'd think carefully about it.