The nice thing about mathematics is that there probably won't be any failed or non-reproducible experiments in the lab. That doesn't mean that a math PhD is going to be easy, but you should be aware that a lot of people will have a different idea of what you are doing if you don't tell them that your PhD is in math.

Best of luck for your PhD! You might want to check out this ted talk: https://www.ted.com/talks/uri_alon_why_science_demands_a_lea...

From what I've read, graduate study on your side of the pond is a lot better than in the US. I really can't say why. The people I know who got their PhDs in Scotland were, for one thing, really sharp. That helps. For another, it seems there's more of an expectation of a difficult but manageable workload and risk level. Maybe more focus on research and less on politics. Of course, a better safety net, meaning less pressure to drop out if something happens like your spouse or child needs medical care.

Every country is different.

If time and money weren't concerns, I would love to do mathematics research!

I hope you achieve good things, and have fun while at it!

I hope you have decent source of secondary income or your family is reasonably well off.

A math PhD might take 6-7 years to complete and I hope that, at the end of it all, you won’t have to come to London to look for C++ or Ocaml jobs at hedge funds or banks.

There is literally an ocean of difference between mathematics and ML (which seems to be what a lot of comments are talking about).