I've put myself in part time slots and haven't had a problem even though I'm full time. It's more of a deterrent but unless things have changed, I don't think they can stop you enrolling in those slots.
Econ111 is a gimme subject if you've done HSC Economics, if you haven't, it still is a 'easier than some' subject to pass.
And for Mark101, turn up to all the lectures and make sure you get the lecture notes because if you have Venkat (which you most likely will), he'll be a bastard and only post skelleton slides on the net, and the exams will cover stuff only taught exclusively in the lectures.... it's part of their approach to improve lecture attendences.