I'd like to go back to uni and become a project manager at some point.
I am wondering where and what I should study? (talking about master's degree here).
I guess Business Management, or International Business Management would be something to consider...although I have also looked at Strategy and Leadership Studies and LMU. I am a bit lost.
If you have the right business experience, an MBA might be the right thing to do. That will give you a wider perspective which would be useful for project management, but would also keep your options open and give you a recognised business qualification. Many unis will offer these so it's just a matter of looking at the detailed syllabus online for a range of unis, to find one which suits you.
If you're focussed on project management, then you can find MSc Project Management courses with a quick Google. Again, you'll need to trawl uni websites to find the one which fits your current experience and situation. The first one I found was Manchester, but that's part-time, designed to be studied whilst you work, and they expect your fees to be paid by your employer. http://www.manchester.ac.uk/study/masters/courses/list/04392/project-management-msc/ It may be a bit specialised for your current situation, but you don't give any details of your background and experience so possibly not
www.findamasters.co.uk is a good search tool to start with if you don't want to weed through Google results.