A
portal somewhere in/near the homebase would be good (but not where it can be hit by a creeper).
I must have been getting confused from warping, I thought my skybase was much nearer to the homebase as I would get there from warping to town1, but town1 is in a completely different place to where I thought it was (which is where the other town on the map is). It seems as though I have a direct line back to the greenhouse, so I will set up a massive underground tunnel next