Thanks Richard,
Just had a look and I can indeed see the flap moving with the control knob,
You can also see the bottom of the heater matrix .
What it has shown me is that my flap is neither closing nor opening fully as I can just reach it with my finger and move it a bit even when the knob is hard over open and closed.
I suspect the control quadrant detents need cleaning as I've seen in another post somewhere on here.
Certainly answers why I always get some hot air even with the knob suggesting fully closed.
Thanks again Richard, such a simple check but it reveals a great deal.