Bit of plastic (trim removal tool or screwdriver with cloth) to put between vent and dash and just lever out. Once you can get to the edge just pull. Vent surround and vent will come out together, you can unclip the surrounds once vents are out.
Done the roof lining with a similar fabric and sick of the sorry state of the flocking I've got on the A-pillars and lower dash, so this seems the logical next step!
