The seats at The O2 are quite steep anyway, so it might be ok.
But you are quite direct to the side as opposed to at an angle to the side so that might be a problem.
Either way, its better than being on Level 4.
I was on level 4 last week for Michael McIntyre, and you can hear perfectly, and as long as the screens are on, it's fine. Everytime I've been I've sat somewhere different, and the viewing hasn't been much of a problem.
You'll have a bit of a side on angle but aside from that it'll be a pretty damn good view, I've sat in 104 and 106 before and the view has been fine and you're even closer than that. Literally right alongside the stage.
As someone before said, the incline at the O2 is very steep so it won't matter that you're at the rear of your block.