Thanks all - that's really useful feedback to have; for either of the roles (business or data focused) I would be tempted to get some sort of formal recognition for my training as it's only a part of my current job, and the likelihood would be that I would have to move companies to pursue a career in this area - and it probably would appear better if I have something (regardless of level) that confirms training & competence in areas - from the feedback given it generally seems that SQL, Python & R would be useful.
Just a note - Business Analysts aren't necessarily more business focused... it's often the other way around actually. Business Analysts are frequently (but not exclusively) under IT head count and involved in writing specs for IT related stuff, whether software or otherwise. You might also see them referred to as systems analyst too... the Oxford course would probably be ideal for this sort of role. So a data analyst that is also kind of a business analyst could also be quite IT focused and involved with writing specs, liaising with developers and with stakeholders on the business side etc..
Other data science/data analyst roles might be unrelated to IT or IT/software projects... they need to code etc.. but they might well fall under the business side itself rather than IT. For example a friend of mine models and forecasts house prices, he's got nothing to do with improving any systems, getting involved in data driven design, writing specs etc.. beyond implementing his own models.
Of course just to muddle things further - there are data science/analyst roles that are very tech focused... but not necessarily involved the business analyst/speccing stuff part... see any number of roles in big tech firms, or indeed things like detecting credit card fraud in retail banking, reporting on click data/marketing etc.. etc..
I'd be starting from scratch when it comes to qualifications (I asked recently about whether I should resit my Maths GCSE as when I did it many years ago I did not particularly cover myself in glory), but I see that the OU does an intro to mathematics concepts that then leads into data science related qualifications. I also like the look of the Udacity course - but need to work on my Python before I can go for that.
It could be a long process - beauty is though that if you enjoy it then you can just plod your way through part time.. I mean just getting some basic skills doesn't necessarily take too long, I don't think you'd need to spend too much time learning Python in order to get to the point where you can tackle say a Udacity nanodegree, I'm pretty sure they have standalone introductory courses if you search around on their website too. Something like that would seem to be a good move to just get you started/get to the point where you can do stuff with data.
There are a wide range of roles involving data, some attract average pay, some are possibly the highest paying careers/professions available.
This isn't actually anything new either - when you start to learn statistics for example you'll come across, for example, Student's t-distribution - this was created by Willam Sealy Gosset, a "data analyst"/statistician working for the Guiness brewery back in 1908! See also the insurance industry, they have made use of data analysts for centuries - they're called actuaries and they have their own set of professional examinations, this is probably the highest paid profession out there.
So basically you could get some basic skills now and try to land some sort of job doing *something* with data, perhaps you stop there and/or just end up learning new packages (business intelligence related stuff, become more proficient in SQL etc..). Alternatively, you can carry on studying, gain more academic quals... this could take the next decade.
I think UoL external system and Birkbeck will require A-Level maths, I guess the OU might be possible though starting from scratch - it could take you 4-6 years from next September to get a degree. Then if you want some of the more serious roles you'll generally need an MSc too - that's another 2 or 3 years part time, alternatively if you train to become an actuary that is at least 3 years IIRC (in theory you don't actually need a degree to become an actuary, just A-Level maths, but most are graduates IIRC).
If in 10 years time you've got 10 years of python, SQL etc... and applying statistics to business problems + BSC maths/stats/data science + MSc in similar from a good uni... you'd probably be very very employable by then.