While you may not be solving partial differential equations in your average tech startup, there are plenty of instances where a maths degree can be directly applicable. Statistics is one instance, for A/B testing. Another example is the use of vector calculus in machine learning and "data science".

How did you find the OU degree?

It was good. I took it almost as slowly as you can (typically one module per year) so it was 8 years from start to finish. In that time I got married, moved house twice and became a father so I wanted to avoid it taking over my life. Tutorials were local to home or work (I was lucky in that respect) but they did seem infrequent.

Tricky to recommend now the fees have quadrupled though (I paid about £4k in total for my degree, it'd be closer to £15k now); unless it's your first degree and you're considering the OU over a traditional university; then £5k a year is quite cheap as you can be much more flexible with life and (part/full-time) work.

I was considering either continuing with the OU with Maths on some of the Master's courses (those fees aren't subsidised in the same way that UG courses are), or switching to languages (French, German, Spanish) but the prices put me off those. For now I'll have a year or two off as a break.

Sorry, somewhat OT but wanted to chip in on this as I'm actually into my 3rd year of a (hopefully) six year BSc in Mathematics. I find the course material really well presented. I've been taking it far more seriously and enjoying it far more than my very first degree (which I had a hard time of). The mathematics department is considered somewhat 'backward' compared to the others as they're one of the few that mandate the postal submission of 'TMAs' (tutor marked assessments).

You are compelled to do certain computer parts in Mathcad, which isn't too bad if you use Latex. I tend to develop and study using Scipy however and then do final bits in whatever software I need to. I've put up some code for my own use here https://github.com/jaymzcd/oucode/.

Totally agree with the other comment around fees - I'm "locked in" to transitional arrangements meaning my total degree cost will be approx ~£5k. Had that stayed for all I'd have no qualms recommending it; now it's quite a bit more expensive I think you need to weigh up what you expect from it. Still, I think it's been a great decision to go for it; it's hard work combined with a demanding full time job but the glow of the mental accomplishment is great.

I don't exactly need to know how to solve differential equations to build a Facebook tab but it keeps me constantly thinking of new ways to do even simple things. I did use some of the knowledge of t-tests and sampling from my stats course to quantitatively report whether a stats rise after we launched a competition was the cause or if it could be considered random. Not exactly required but it did read and sound impressive on the slides we sent the client.

As an added bonus I also save ~ 30% on my TFL London travel card as you qualify for student support even with the OU; which actually, over a year, accounts for around 60% of my actual module cost!

I was hoping you would also recommend G.H Hardy's Theory of Numbers