"The "sent by road - already fuelled" bit may sound scary - as in, what if someone just nicks one and drives off with it."
I'm not worried about theft, but road collapse. These trucks would be heavy AF. What happens if the road gives way under one side and the truck falls on its side? A whole lot of road closure.
It's also a much better idea to get the installation done and properly tested before loading fuel. You don't want to be chasing down leaks on the hot side that opened up during transport.