Just how important is triple accreditation or even a single one? Would studying in an uncredited school not offer much of a return on investment in the long term, or does this vary depending on the country/industry? I've been working in the tech industry and would like to further my career there, but I can't relocate, unfortunately. Where I live, the two options I have are uncreddited.

This depends on your goals. Additional accreditation is a mark of higher quality and generally leads to better outcomes. If you want an MBA level role, in a firm that recruits MBAs, or want to move industries, then a better programme helps. 

Look at the people in the role, industry and location where you want to work. What qualifications do they have?