What has been added and/or changed in the 2 Gurren Lagann movies compared to TV series?
The first movie (Gurren-hen or Childhood's End) is basically a recap of the first half of the tv series, similarly the second movie (Lagann-hen or The Lights in the Sky Are Stars) covers the second half.

There is around 20 minutes of new material in the first film and a bit more in the second film - primarily added in the final battle

The only changes in plot were that


   Makken doesn't die


&amp;


   The Gurren Lagann evolves to an even higher stage, becoming Dai Tengen Toppa Gurren Lagann which is even larger than galaxies!


There's an overall improvement in the animation quality, noticeably making battle scenes more thrilling.



also seemingly Yoko's breasts are slightly bigger in the movies ref.