SMC/BMO is a really bad example because it's a very specific type of problem-solving skill. STEP is probably closer to university standard. Basically, it's A-level maths, but much deeper, much more extended, and you're not expected to have your hand held all the way through the problem.
An example of a sort of vaguely university "standard" question (made up off the top of my head, admittedly

):
"Prove, using the focus-directrix property, that the sum of the distances from the two foci of an ellipse to any given point on the ellipse is constant. Hence show that..." (This would be the first, easy lead-in part to a longer question on a first term paper.)
The A-level equivalent:
"E is the ellipse x^2/9 + y^2/16 = 1. The foci are F and F'.
(a) Write down the coordinates of F and F'.
(b) Show that the ellipse can be parametrised as x = 3 cos t, y = 4 sin t.
(c) Using (a) and (b), find expressions for the distances FP and PF', where P is any point (x, y) on the ellipse.
(d) Show that FP + PF' = 6. [12 marks]" (Probably on the harder end of FP2.)
*shrugs* Something like that.

And of course you learn loads of new material... but you knew all that.