I currently study at the City North Campus and live at The Coppice
The Coppice and Oscott Gardens are both literally across the road from the uni. Both are lovely halls, but as Oscott is more expensive they get sofas in their kitchen/lounge areas, and en-suite bathrooms. Not having en-suite is no problem at all thought.. people worry about it but its nothing different from how you share a bathroom in any house - theres rarely any problems! (and two bathrooms in each flat in the Coppice anyway)
To get to town from there it costs about £7 in a taxi, or you can take a train or bus for £2 return, both take about 20 mins each way. It's not that far from the centre at all really.
And all those who say its a 'dangerous' area are telling lies, theres absolutely no problems living here, we have our own on-site security and everyone who lives here are students anyway. It's not the best idea in the world to wander into back streets at 4am on your own, but then again it's not a good idea where ever you live.
As for other accomodation, I have only visited Jennens Court, which is the best I've seen, and is right in the center of Brum. Again, slightly more expensive but it's worth it