While I thoroughly support the idea of mature students, and always believe in doing something you are actually interested in, I just thought I should say that if you want to know about career prospects in those fields here may not be the best place to ask because the majority of people here will be younger and, while they might have experienced the difficulty of finding a job as a graduate, few will have experienced the difficulties that can present when you try to find a job as a much older graduate.
When competition is tough, they're going to look for people who they can hopefully retain for a long time and develop in the company. And people with plenty of experience in the field.
My dad was made unemployed a few years back and he is now 58. He has a reputable degree from the OU and experience which makes him well qualified for the types of jobs he applied for (laboratory technicians in schools, factories etc) but he has only ever since had sporadic work and he believes that his age is a factor in this.
Now of course, I'm not clued up on law/engineering. Maybe if you already have some experience in these fields they would welcome you with open arms. I just, y'know, thought I'd mention it.