If you want to have a successful career change, do a degree which is designed to lead to a specific job, e.g. teaching or nursing, which seem to be the most popular options, and potentially law or accountancy, although do your research first. You might become a soliticitor but it might be much harder to become a barrister, for example.
Don't bother if you just want to take a "general" degree, English Literature, History etc and aren't sure what job you want, just that you want a new job, any job, because you're generally sick of where you are. I did a Geography degree and although I'm very glad I did it for a whole host of complicated reasons, it was of fuck all use to me in getting a graduate job. There was a career path I was interested in, but I was basically told to sod off and stop bothering, so I gave up. Looking for a graduate job as a mature graduate in your 30s is very, very different from looking for a graduate job as a 21-year-old who's taken a more traditional path.
I had no idea what I wanted to do, just that I hated my life and most employers were asking for degrees, so I did one, hoping that I'd find a niche interest and do a masters in a more career-focussed course. I never did a masters in the end as I'd become so disillusioned with the whole thing that I gave up.
Sorry to be so grumpy today but in my experience, "Just get a degree, any degree, because employers like graduates" just doesn't work the same way for mature graduates.