Prof Stephen Hawking: man faces nuclear armageddon and must colonise space

[Maslo55]

18. ...

Implying that would not be human presence, which would grow over time if access to space was not very expensive. Implying it is not enough to expand our presence at least into the inner solar system (I am skeptical about colonising other star systems due to FTL barrier, but colonising our solar system is perfectly viable with our technology).

SpaceX rockets and capsules, Atlas Phase II, factory produced Bigelow inflatable modules, fuel depots, ion thrusters, maybe nuclear powered outposts and nuclear propusion - with these things we can build human colony on the Moon or Mars for fraction of the ISS cost. If we wanted.

(substitute Skylon with 20 ton to LEO EELV if Skylon does not deliver in time)

Your estimations are based on outdated economics of rigid modules, horrible Shuttle cost per lifted Kg and habitable space ratio and absence of fuel depots and ion cyclers for consumables.
Not even talking about the huge decrease in lifting costs when reusable rockets (Grasshopper) or Skylon delivers.

We have, or would have in the near future the technology to economically colonise at least the inner solar system. People think that manned spaceflight is very expensive because they judge it based on failed Shuttle economics, bad political decisions and other things mentioned above. Its not the only way to do it.