Due to the proximity of residential flats, photography is not allowed from the external viewing gallery. But the views through the window from the cafe itself are still pretty good.
The cafe itself is fairly standard as museum or gallery cafes go, though it has the advantage of being neither the big ground floor cafe, nor the one in the other block on Level 6, and so is much quieter. Plus it has great views.
You can see all my cafés with view in London here.