Issues with air vents

Hi all!

I've not long bought my Mk3 Octavia VRS diesel, and discovered a strange issue with the air vents. In short, the passenger side vents don't blow as strong as the drivers side vents.

The drivers vents blow nice and strong, but the passenger vents don't, especially the passenger vent in the centre console, which barely blows at all.

As if that wasn't enough, the two centre vents don't blow hot air! It comes out barely luke warm with the heaters on full, whilst the outer two vents blow air hotter than Ghandis flip-flop.

Things I've done:

1) check the vents are actually open

2) re-calibrate the blowers

3) check pollen filter (last replaced less than a year ago)

I've read somewhere that the airflow is controller by some sort of "air distribution flap", which could well be the issue, but I'm struggling to find the right part, or a guide on how to fit them.

Any help? Thank you!

Tim