Difference between economics and finance?

They aren't really related at all. Economics is in a dictionary definition sense the study of allocation of scarce resources. Finance is studying how to grow capital in business contexts. More specifically economics will develop general economic theories to account for economic phenomena in the world, in finance you just...learn about (mostly corporate) finance, how companies manage their finances, make investment/trading decisions, the various laws and regulations surrounding that etc.

They're about as related as say, physics and computer science. While there are some common methodologies used by both, and in a very general sense the theoretical framework of one gives rise to the other, but they are largely independent subjects in reality.

So investment funds mostly fall under finance? So in the real world how would economics be applied? Similarly how would finance be applied? And which is more maths heavy? And which is more valued in the job market? And by whom?

Nobody in the job market (at least, in most general "business" or financial services grad schemes) cares what subject you studied, unless you're applying to roles in e.g. engineering or healthcare where you need to have a particular accredited degree. Since this seems somewhat transparently to actually be "what should I study to be an investment banker" the answer is it doesn't matter whatsoever as long as you go to a target uni and get relevant work experience. If you go to a semi-target or non-target your odds are much worse.

For the rest of the vast majority of generalist grad schemes in business, media, accounting, the civil service etc it doesn't matter what you studied. Two people I know went into Big 4 accounting grad schemes; one did engineering, the other history and politics. Literally did not make any difference (also neither went to target unis, which is only relevant for investment banking and consulting).

Which degree is more maths heavy?

Which degree is more maths heavy?

Depends where you study it and the exact content. In general I would expect economics to be somewhat more mathematical by necessity, but there are some less mathematical economics degrees, and some more mathematical finance degrees (e.g. LSE finance vs Goldsmiths economics).

I would assume economics would be