As far as your questions about the terrain and a couple of examples of the casualties (both British/Canadian, as well as an example of a German unit in the same area), the documentary "Battle Of The Somme - The True Story" appears to be good resource. Personally I think that this is one of the best documentaries about the Somme that I've seen from a historical perspective in so much as it tries to tie the big picture to the personal level. It also doesn't consider the German side of the battle in some distant, passive sense -- but instead looks at everything from all sides to understand how the pieces fit together. I was shocked to see how much of a hole the British/Canadian positions were located in. I've never been in the military, but they are pretty obviously a very bad location from which to launch an attack.
Here's a link. Note that in the auto-play sections 6, 7 and 8 are not in the correct order.http://youtu.be/KgPcko8XLKE