Mate,
Aviation has taken me all around the world. I do it for a living full time and I enjoy it.
I'm from New Zealand and I have flown in Australia, Botswana, Canada and now Indonesia.
The stories that I can tell from my short life already puts most peoples entire lives to shame.
Aviation is what you make of it. If you want to race for the big jets, then you will probably get bored aviation rather quickly and wish that you had followed the Maths path.
If you take what is on offer around the world, it can take you to places and show you things that you didn't even know existed.
My one piece of advice. Whatever you do, don't rush. You are 18. You have nearly 50yrs of flying or work ahead of you.
Do your maths degree, have it in your back pocket to fall back on. Start flying and make a go of it.
If it doesn't work out, use the maths thing and fly when you can.
Just don't rush.