I did three years of an undergraduate degree in Philosophy at Southampton uni, only to come away with my first year...a huge pile of debt, desperately depressed and only my first year under my belt. I hated the course, had no ambition, no end goal and basically no chance! I was too stubborn (stupid) to admit that i'd made a mistake and failing my second year for a second time, the decision to leave uni was made for me. 5 years on and I have worked in loads of different jobs and given myself time to decide what I want to do. I finished my BA (in a different subject!!) through the Open University whilst working full time, and after some voluntary work in a number of schools I am now enrolled on a PGCE primary course for this coming September. I couldn't be more excited! I wish I had had your determination and not convinced myself to limp-on in something I wasn't enjoying. I had no help from the so called 'jobcentre'; they are sole-crushing, patronising, power trippers who want to hit quotas not help genuine job seekers.
So from my experience, I think you'll be fine either way. If I had never gone back to uni I would have been fine - as I managed (after a fair bit of searching i'll admit) to settle in to a job that I loved just through my A-levels and could have taken me places had I not settled on teaching. And the fact that I did go back and successfully complete it told me that I was able and it just took finding the right drive/situation. I thoroughly recommend distance learning, I had more contact with my tutor most days than I had each week at a Russell group university (go figure!). and completing my final two years cost less than half of one year now! Trust your instincts, I wish I had!! Best of luck