Right... Firstly id mask off the vent indents on the dash just uncase you slip!
Take your radio and centre Tray out.
Remove two Torx T-20 screws from the left and right of the fascia and 2 i think from above (use a torch!)
IF you have climate, youll need to remove two from underneath either side of that. Either use a small screwdriver/wrench or take out your ash tray so you can get enough room to put your driver in.
Take the fascia out. Unplug the Rear demster and airbag light.
Now with the whole lot out, theres now space to get your hand into the centre vents. Use your fingers or be careful with a screwdriver to pop the vents out by pushing them toward the rear of the car. When theyre out you can use a screwdriver to gently unlip the surrounds.
When youve done, make sure the vents are straight and the small lip on the chrome surround lines up with the one on the dash and simply push in untill it clicks, guiding it in correctly with your hand behind the dash. If you come accross resistance at this point, the vent is not quite aligned with the rubber pipe so try giveing it a wiggle!
Then re-assemble your dash.
Oh and cheers Tom