Annoying clicking every 7-8 minutes

[A8essex]

Arrrhgg....drives me mad. Must be 25-35 clicks in quite quick succession from behind the centre of dash and sometimes it seems behind/below steering column (RHD UK spec D2 2000MY)
Also noticed the centre vents have very little (almost none at all) air coming out even when fan is on max. Sometimes flipping to AUTO the centre ones seem to work some more but when next in car its back to nothing. (the very middle vent with the hot/cold slider works, tho is never hot)

So am guessing that maybe the centre flaps dont open properly and the clicking is related....though why it does it every 8 mins is a mystery.
Its done this ever since i got the car !...any ideas?