Hi,
I'm just about to graduate from York with an MPhys in Theoretical Physics, so I've spent 4 years in the department.
The teaching is generally excellent, in particular the lecturers and demonstrators you'll come across in your first two years are brilliant. As you go into third and fourth years, the lecturers you meet become more research based, so teaching isn't necessarily their strength, but they are still very good.
Every year (even first year) you get to pick optional modules based on your interests. In my first year I was actually on the Experimental physics route, but after taking an optional theoretical module and seeing how interesting it all was, I was allowed to change to the theoretical physics route. So very flexible.
I did two internships in the physics department over the summers of my second and third years, both funded as well (a nice treat). Lots of other people do internships within the department, while others go into industry for the summer. There are dedicated staff members who are there to help you with internships and other employ-ability matters. You could also do a year in industry if you wanted.
Obviously since it's physics there is an unfortunate skew towards male students in the ratio, but there are quite a lot of female students too, I'd say around 3:1 male:female. This isn't something I noticed majorly, but that's probably because I'm a clueless male.
York is a beautiful place to live, although it does get busy with tourists on the weekends. The university itself is actually outside York in a village called Heslington, so you're shielded from the bustle of the city for most of the time.
Hope that helps!