What do you mean by away placements? Can't your uni accommodate you and give you placements closer to your home/uni?
Do you work on top of your nursing degree? With OU most of your placements will be at your base (place of work, your ward etc) but you are still expected to gain other experiences such as community/surgical if you are based in medical. Like Melora said, you must be in suitable employment and employer must agree to support you.
Sorry I can't compare to brick uni, but I don't recommend OU. It's hard, there isn't a lot of support and you have to work your contracted hours, fitting study time in when you can. You don't get breaks like you would at a brick uni, it is relentless. I am biased, I'm half way through and miserable at the moment. Theoretically it is more flexible, but it's stressful and grades suffer because you don't get sufficient time to study unless your employer gives you study time (mine does not).