My understanding is that if you want to do a nursing degree (ie train so you're a nurse at the end of it) with the OU, you have to be working as a healthcare assistant or similar, and have the support of your employer to undertake the course. This is because there are a lot of very hands on, practical aspects to nursing, and the training requires that you spend time working with patients in a healthcare setting. So, it's not that an OU degree is inherently something you won't be able to get a good job with; it's that this specific job requires specific training.
You could, possibly, look at whether you could do an OU degree in a related subject - like Health & Social Care, perhaps - and then do further 'accelerated' study elsewhere after you graduate, to qualify as a nurse. I believe this would take another couple of years (full-time). You'd need to check whether the course you were doing initially would be acceptable to accelerated programmes, and to look into the funding arrangements for doing this, though.