I don't think they have anything to appeal. If lewis told them "he slowed down to read his display", and the radio recording said "slow down let Trulli past" then he has lied to the stewards, so they sits the judgement. He miss lead the Stewards. nothing to appeal
If you look at "Transcript of McLaren radio transmission" on autosport.com, you could say the "slow down let Trulli past" is negated by next exchange. "Stay ahead. We will get back to you. We are talking to Charlie." LH: I let him past. This is so ambiguous, did Trulli pass LH to regain 3rd position without Lewis really intending it. And for the race director to ask LH whether he had consciously allowed Trulli to overtake, I can see two points of view for Lewis. The stewards asked a gotcha question and either intent by Lewis or team would be misleading according to pre-determined rules of FIA. 
Team "Slow Down let him past"
Lewis slows down an lets him past
Team "No don't let him past"
oh dear damage done.
Stewards "did you let Trulli Passed?"
Lewis/Mclaren "no"
replay tape, oh dear.
I am not really sure why Mclaren had to brief Lewis on the way to the meeting.... Could a driver really not remember what happened? unless McLaren set out to lie.
I think Bruce would be spinning in his grave
