I did an OU degree in Psychology while I was working. It is a very flexible way to study and they are very well set up for distance learning. If you want a degree that is recognised by professional bodies, your subject choice is slightly restricted. (Eg Psychology was guided by the BPS).
This helped me spring board into CRM instructing. I'm about to start a Masters in Aviation Human Factors at Coventry Uni. It's all distance learning which suits me.
Why Psychology? Human behaviour is absolutely integral to how the flight deck operates but more importantly, we're humans and understanding how we think and interact was very interesting.
Good luck
