Looking for stories where the Ministry falls and everyone rallies at Hogwarts, turning it into a fortress from which they can fight out of. The bureaucracy, the DMLE, families all try to relocate there. The stories usually feature large scale warfare instead of the guerrilla action normally favoured by the underdog in a story where they don't have a redoubt.

I know these were quite popular before HP7 came out as I think a lot of people expected the book to follow this line. I'm hoping to find something a bit more modern though.

 

The only thing that immediately leaps to mind is Thalarian's Seven Ladies of Darkness, Seven Ladies of Light. Very old, has not aged super well, but is still readable and has a lot of cool concepts.

 

Silently Watches 4 part series ending with The Black Queen's War has exactly that. Its also a great read with 100's of thousands of words.

 

Is that the one the one that starts with Princess of the Blacks?Because unless the later stories are dramatically better then the first one I can't recommend it.
There is a reason it sits at 1.5 stars at the moment. And the pedophilia stuff in the first couple of chapters isn't even it.