Yes, I think it's made clear that Desmond sails to England (from where, I don't know). And from England, he sails to L.A. It definitely is a huge chore for the character, but I have not seen anything to indicate that it's inconsistent with the timeline.
It kind of makes me laugh though when I think about all the grief poor Desmond is put through. And he does all this pointless travelling, for what? I remember thinking when Widmore writes down the address for Farraday's mother in L.A., why the hell can't he just give the poor bastard the phone number?! Wouldn't that have been much easier for everyone. Plus, wouldn't that be more in line with Widmore's wish to keep his daughter hidden from the dangerous business?