I've done it so many times to dry out my old leaky headlight...
Here's a quick summary, though there are better guides! You can do it without dropping the whole bumper, but it's a fiddle. Sorry I can't remember any of the screw/socket sizes, but if you've got a half decent set you'll be sorted.
> Turn the front wheels to full left hand lock
> Undo the two phillips screws holding the wheelarch liner to the arch
> Pull the lining out as much as you can around the bumper and wing
> There are two hex screws attaching the bumper to the wing, behind the wheel arch liner. Get on the floor and look up inside the bumper from the wheel, you'll see them. One screws right into the wing, the other has a nut and a couple of washers - don't let these drop down onto the undertray!
> There are 5 (I think) screws holding the bumper to the underside of the car. Two are right infront of the wheels, and the other three (or four) are at the front. Cant remember the size, but you'll need a spanner or socket.
> The last four screws are at the top of the bumper, where the bonnet closes. Think these are hex too.
>Once all those are out, gently pull the bumper off from near the wheel, and pull it out a bit. It'll bend quite a bit, and then just rest it on the floor.
> There are three screws (socket only for these, spanner won't fit) holding the headlight in. Undo these, and then wiggle the headlight out. There's a bit of knack to getting it out... you want to kind of rotate it clockwise (looking down from the top) as you pull it out, and lift the bottom up a bit.
> Unplug the plug going into the back. On the xenons you slide up the yellow thing, and it'll just pull out, not sure about halogens.
Then the reverse to reassemble. When you're putting the bumper back into place, make sure the foam things behind it don't get in the way, you might need to slide your hand down behind it to move them a bit.
It's a bit of a pain tbh but once you've done it a few times it's okay.