Doc, I want to drive your Celica badly! oh and welcome new guy, cool taste in cars. My buddy had a cressida, he used dry ice to get the sound deadening out, it saved a ton of weight!
From the factory I think the S4 is a good sleeper, like the C4 S4 or B5 S4. If we are talking a modded sleeper - I would say the Colt minus the cage, Sam's E30 without the big ass tires in the back! lol.
I don't know any of the land rover service guys over there, I can ask one of my friends over there and see if he is able to perform the update with any of the computers he has in the main building though.