AthersI'd recommend Treble Cone, Craigieburn (my personal faveourite), Mt Olympus and Temple Basin for BC/Steeps. Treble Cone is down near Wanaka/Queenstown, the other three are kinda in the middle of the island, circa 90mins to 2hrs from Christchurch.
TC has propper lifts and groomed slopes, the other three are completely ungroomed and have nutcracker rope tows only (sounds a bit crazy but not too much drama on skis - does require a harness or belt though. Check Youtube for vids).
Hope that helps!
Craigieburn is a personal favourite of myself and also Glen Plake, who actually joined the Craigieburn Valley Ski Club because he liked it that much. The club fields are a unique experience so definitely check them out if you're into steeps.
Here's an article I dug up with a part about the club fields by David Lesh