Wotwotius, I 'm definitely not trying to pick on your initial post but here is one of my issues:
Much more likely was that the misgivings had to do with the fear of getting swallowed up by Oceanus, Neptune, Triton, etc. as naval crossings for an entire army were risky business; regardless if it was Sicily to Africa, Italy to Greece, Italy to Spain or Gaul to Britain. Furthermore, whay would they think they would sail off the edge of the world when they knew that the famous G.J. Caesar landed there. Another more than likely was that they new that the *great* Caesar didn't have an easy go of it 'over there'
I will concede however that there were bound to be some superstitious and ignorant folks who would see a 2D 'map' and take that to be a true representation of the world. The exception however, not the norm enough to halt a campaign.
*Edit: 43 AD, not 44 AD (i think I wrote that date twice ).
When I wrote the above post, I was referring to the uneducated poor, who, by in large, made up the vast majority of Romans (and thus the vast majority of her legions). I also stand by my argument that most Romans assigned themselves