lowest cost part time uk (or maybe EU) academic degree

pjread

So, I don't need to do another degree for any pragmatic or career reason, I'm "sorted" in that regard and happily studying various MOOC's or similar for essentially recreation.

That said, sometimes the odd course has bits where I could benefit from being able to incentivise myself to put in a bit more effort and a 'reward' at the end of it all would help me focus at these points.

I'm an OU student but it's far too expensive to do 'enough' OU to fill my rather long commute throughout the year, so I was wondering if there was something lower cost but not 'worthless' - in terms of I do expect zero practical value in reality, but don't want something that'd be laughed at if I ever wanted to rely on it (e.g. to pursue postgrad in the field in later, later life, like post-retirement). Only interested in 'proper' academic subjects for the most part, but very broad brush within that - physics to philosophy, astronomy to geology are all good, not one for too 'fluffy' a subject though. Distance is a must though as I want to study primarily during a 4-5hr round trip rail commute.