Thanks IcePack and Heinz. That link to the heater control post does show the removal on the vents and a lot of other info as well.
The vents were relatively easy to remove (following Icepack's instructions) and certainly gives good access to the flap and Bowden cable.
I've actually taken some photos inside but they are inverting when I upload to TMimg which makes them quite confusing to view. (See my plea for help on another post)
I think there are actually 2 flaps in there as I can see the main Bowden cable connection that operates the front flap but then there is a linkage to a second flap that seems to operate some thing at the back of the heater box. (looking through the vent)
A picture paints a thousand words so I will post if I can solve the inversion issue I have.
