Entry requirements are often different for mature students, particularly if you have been working in a related field, so it is worth you checking if you have a university of preference.
I am not clear on exactly what you are looking for from the university degree. If you just want to step up your learning and don't care about the piece of paper at the end, then enrolling at a university is unnecessary. The main benefits of being on courses are not that the lecturer will teach you amazing new things you won't find anywhere else. The benefits of being on a course are:
1) The lecturer will structure it to separate the important parts out for you (this is very important, because there is always too much info, and you could spend the rest of your life just reading economics books)
2) It can add discipline because it keeps you working each week, and revising for an exam
3) You have others also working on it with you which helps (and access to the student bars
)
But, the main one for learning is 1), and for that your best bet is to look at a top university's web pages. Lots of them will produce course pages which will list the important topics, and recommended reading, and that gives you the important stuff.
I recommend you check this out
Free Online MIT Course Materials | Economics | MIT OpenCourseWare
Click on a course and there will be a "download course materials" link on the lower right. These will be of varying standards, but MIT is not a bad university
. There are actually a lot of free resources online from top universities around the world.
