SUCCESS!!! I finally got around to this. No photo's unfortunately as even with the wheel arch off there is not much to see.

The bulbs fit. As I suspected BMW is re-using the old parts bin.

So here is a run down of the steps:
1. Make sure you have a plastic rivet gun and plastic rivets for the front wheel arch/guard. Also the other screwdrivers etc.
2. Remove the wheel, followed by the wheel arch being careful of the brake lines, sensor lines etc.
3. Get up in there with a Phillips-head screwdriver and remove the 3x screws holding the rear cover behind the park light.
4. Remove the rear cover.
5. Brace yourself...

THAT is the easy bit. Getting the old bulb out and the new bulb in is the HARD part. The stealership manual says to remove the quarter-panel as well to basically remove the whole headlight module to replace the park light... pffft.

1. There are two screws deep in the body of the headlight housing holding the OE part inside to the light guides of the halo's. These are located in the middle of the 3 holes top and bottom. Funnily enough it doesn't matter what I say, this is done by braille. You can't see inside the headlight housing to see what you're doing anyway,
2. Take off these screws with a magnetised screwdriver, you will loose the screws otherwise.
3. Disconnect and carefully remove the OE part.
4. PROTIP: get some silicon grease (not sealer) and put a dab on the screw guides on your LED upgrade. This will help keep the screws lined up for the next step.
5. CAREFULLY guide the LED part back into the housing and then get the screws lined up and tapped.
6. With both screws tapped, tighten up and connect the power. My bulbs had no + or -, so it must have a smart relay inside to keep the power in the right direction for the LED.

TEST and then put the cover and wheel guard back on.

BONUS PROTIP: Don't forget to put the wheels back on before you drive off.

Attached is:
1. A pic from the view of the low beam headlamp cover of the PITA in question. If you've got a mate who can spot for you or hold the bulb while you screw the screw's it might be easier.
2. The cover you need to reach through the wheel arch to remove.

Attached Images