Ok all you techs out there.
What is the best way to remove the fill Plug on the transfer case.
As I tried a 13mn socket and ratchet today and there was not enough room for it to fit.
I'm thinking a 13mm ratchet ring spanner.
Is this how everyone else is removing it?
Please bare in mind I'm laying flat on my back under the car.
Does anyone have any advice or photos?

I did it exactly the same way, I seem to remember that I used a ring spanner and had to give it some force to undo it, possibly even a few taps from the persuader. The spanner should be below the bottom of the vehicle so you can give it a couple of knocks if necessary.