Lecturer/ researcher; but you mention money, so you may want to discount this suggestion!
If you get stressed out because of AS levels then medicine is probably not for you. Think about working your ass off having to do 1 patient every 10-15 mins while knowing you're being sued by a 60yo daily mail reader for something ridiculously silly. Most of the doctors I know have taken meds to relieve stress at one point or another. Avoid it if you have a low tolerance for stupid people or pick a speciality with little contact with patients.
Generally narrow it to the stuff you'd enjoy doing, THEN think about the money. Not the other way round. You can make lots of money in any field.
Look up Actuarial Science if you're into maths/statistics/finance
Academic or actuary.
Actuary sounds right up your street, actually - fairly tough intellectually, with great financial rewards and [apparently] relatively low stress. That's once you've passed the exams though, so maybe the first few years wouldn't be a party for you!