I do, and assumed that all Mk3's do, but I recently changed my carpet and the underfloor foam that came with it has no cut-out for the ducting, wondered if maybe it was just cups that don't have it, or perhaps cars without climate?
Just in front of the join in the carpet, under the seat. You will struggle to see them from the front, but they should be visible if you peer under from the rear.
Haha i never knew this! But its pointless me looking, no chance my pikey spec 200 Cup with Aircon will have it, i imagine its a Climate Control feature :/