My career path:3-year Bachelor's degree in "Physics with Astrophysics"; PhD in X-ray astronomy; 5-years as a postdoctoral research assistant (two separate posts); got a lectureship at a UK university doing teaching and research in Physics and Astrophysics.
This is reasonably typical. These days, the content of the first degree is not so important - Physics, Astrophysics, Applied Maths all would be ok. "Astronomy" would put you at a disadvantage, since the implication is a non-physical, observational approach; but you would have to look at the course content.
A masters degree or 4-year first degree is usually necessary to get onto PhD programmes in the best places (this has changed since my day). Doing your PhD quickly and writing several publications is usually necessary to proceed any further.
The normal next step is to get a postdoctoral position; preferably somewhere other than your PhD institute. Then after 2-3 years of producing more research papers (2-3 per year), you could try for personal research fellowships. If you can get one of these, or perhaps a second/third postdoc position, and your research is going well and is productive, then there is a few year window in which to get into a tenured or tenure-track position. Getting some teaching experience at this stage is probably important.
For someone on a "normal" career path, it would be unusual to get a University position before the age of 30 (i.e. 8-9 years after your first degree). The large majority of people with a PhD in Astrophysics do not end up doing that for a living.