The ashtray is held in with 2 torx screws.
To remove it, you must first remove your gear surround. Its very simple - just put your hand in the rubber gaitor, and grab the surround - and firmly pull it up. The photo is from my MK5, but its the same principle. Stick your fingers in where the white bits are, and pull up!

The surround will remain attached to the gear stick, but you can pull it out of the way.
Then you can remove 2 x Torx screws which hold the ashtray in.
Once the screws are out, you can simply lift the ashtray out - but be careful as the connectors for the buttons need to be removed. You'll also need to remove the connector for the 12v socket.