Regardless of whether you will actually put a maths degree to use on the job market—which no doubt you could, once you attain it—pursuing one can bring great rewards. I am in my thirties too (mid-thirties now) and recently took up maths again. Lucky for me, I come from the German-speaking realm, where there is a distance learning university that offers a solid BSc programme in mathematics at roughly one eighth of what someone would pay for tuition in the UK. I do not know what options you have in that regard, but if being enrolled in a programme does not seem off-putting to you, it might be worth checking out. I am mostly on my own, so I guess if I were studying entirely independently, I would not be doing much different. There are benefits though that I would not want to miss out on—I get my (bi-weekly) assignments reviewed, there are platforms where your teachers and fellow students are communicating, and, last but not least, there are exams that provide for the 'hard facts' as to whether you have been studying your stuff right. Not to mention the degree you are awarded if you succeed. To me it is beyond question that distance education is the right way for me to do this. Like you, I am working in business software development, and I simply cannot attend a brick and mortar university because I do not have the time, or would have to accept the severe cut-back in income resulting from a reduction of my work hours. (Besides, I have been to brick and mortar before, and not being very social, I do not think I am missing out on the social aspects of it at all.) So if there is any distance education option that suits your needs, it might greatly augment your self-directed learning.