Sounds like your Landy is taller than ours (ours is around 2.3m?) altho I don't remember a height restriction being asked about on booking. From memory, 3m may be tight if its the Habib, not sure on the newer ferries. Is it REALLY 3m? Let's hope the wind isn't against you!!
Seriously, I very much doubt they would leave you on the dock. There were plenty of African cars/trucks loaded to twice their normal height with stuff. And they were pretty professional in changing our ticket when we wanted to return a day earlier, so if you had to pay a difference I wouldn't think you would pay over the odds. I would risk it.
Incidentally, I found Southern Ferries pretty useless last year, so used the Belgian SNCM branch, who were very efficient. I'm sorry, I don't have the no. (altho I think it's on the sncm.fr site) They were also marginally cheaper due to exchange rate.
[This message has been edited by ollieholden (edited 25 February 2004).]