The callipers look the same on the CSS with the same part number from what I can see, just different badges on them so normal GTI wheels would fit as the discs are the same size as PP/R/CS discs.
TD 1.2's would be a good bet as they're painted and won't be affected by road salt quite the same as polished GTI wheels. Plus they're light, fairly inexpensive in 18" fitment and go well with the motorsport theme of the car. Another option would be CS Belvedere wheels if you can pick up a set second hand, I'd imagine even the concrete Bridgestones would be a little more grippy than the semi slick standard tyres in Autumn and Winter but I'm sure there are those that would disagree!!