Thanks for the help guys, I had a bit of a fiddle with the footwell lights this afternoon and came to the following conclusion..

Firstly, about six months ago, I installed the front footwell lights via the BCM and activated them via VCDS. I also coded the car to provide ambient lighting whenever the headlights are on. The footwell light setting was available on the MFD.

I noticed that after installing the door courtesy lights (which required disconnecting the battery, possibly resetting the coding I did to provide ambient light??) the light provided by the footwell light was very dull and the brightness couldn't be controlled through the MFD. When this happened I noticed there was very slight flickering but just ignored it.

Over the last few weeks it has been getting progressively worse so this is what I did today:
- change the drivers side LED that was provided by Bold-Sport with the kit to another LED I had on hand. Same issue. Is the number on what appears to be the resistor a rating? (Bold-Sport LED has '301' on it and spare LED has '351')
- I then tried the original halogen that was provided. With the door open the halogen bulb was at 100% brightness as expected, but with the door closed it was off! And the LED in the other footwell fitting was dull and flickering.
- I then tested with a multimeter when the door was open; 13v as expected... Door closed and the voltage fluctuated between 0.15 and 0.31 volts; just enough residual voltage to light up the LED and change the brightness in conjunction with fluctuation.

Anyway, probably all pointless information for this thread but just thought I would share my findings..