The self tapping screw trick didn't work on my heater box. I dreaded removing the complete dash again so I thought I'd try the drilling and spraying lubricant onto the pivot point.

I unplugged the blend motor plug and used a 9v battery to move / free up the blend motors, all good and moving. I drilled the holes, 5mm so you can see through - sorry but I forgot to take pics - and used the straw on the GT85 to aim the spray. I then with SWMBO's help moved through all the button and temp combinations and kept giving it a squirt while it was moving. I then cleared the faults with the Nanocom. Turned the engine off then on and no faults found. Just need to gas up the A/C now!

Pleased to say it worked!

I did find something out though, the Nanocom reported RHS blend motor as faulty. If I'm sat in the car that is actually the LHS passenger blend motor. I'm guessing I either put the motors in the wrong places 4 years ago or LR report from standing looking at the car from the front.
Mine is:
Blue blend motor RH drivers temp
Black blend motor LH passenger temp
Grey blend motor distribution flap

It might be a bug in the Nanocom. I seem to remember mine was telling me the RH blend motor was faulty when it was clearly the LH one. If you look at the feedback return figures as you change the temperature rockers, you can see which one moves and which one is playing up.

And now failed again. Bloody thing. Heater box will be out this week and put an end to it!