Well I changed the cabin filter on some Megane II's and decided to take a few picture's of my one as I thought it may be of some use to other's.
Now, these are dead simple and require no tool's other than a pair of hand's. The filter is located inside the car, by the clutch pedal.
Okay, first this is the area you will be looking at when your changing the filter:
You'll want to remove the side plastic panel which just pull's off, like so:
Once that's off, you can now locate and remove the old filter.
The filter's bend to allow you to remove it, and goes in and out by the left side of the clutch pedal.
Now, the new filter will not be flexible like the old one at first, so all you need to do is bend it at the cut point's untill you hear a little snap.
Old and new next to each other.
They can be a little bit of a fiddle to get back in, but it's a nice simple 2 minute job