Thanks for the pointers. Much appreciated.
I'm doing a full review of mathematics at the moment. Not in depth, more of a "here's an application of the GCD function" so I know what tools to use to solve specific problems. All this is beneficial for the day job as well who expect to see some value from my time spent even though I'm not being totally honest with the objective to them. Realistically I want to think abstractly in the terms of mathematics and develop some intuition.
Was completely unaware of the Theoretical Minimum series. Thanks for that.
Edit: I'm reading Mathematics: From the birth of numbers by Jan Gullberg as a text. Wonderful book. Covers just about everything and is beautifully written by a non mathematician with no assumptions spared and no education target. In fact the forward is mainly bitching about the education system. Slightly worried I will get distracted by this book but that's never a loss!