It's been in the brochure for a week or two, since they updated it to include the Sportback.
Interestingly, unless it's a misprint, it seems to have a bit more torque in a slightly narrower band than the non-quattro. Also, the non-quattro 1.8 seems to be available with either a six or seven speed S-tronic box. Can't fathom why they'd offer it with both.
EDIT: Seems the 7-speed is a full £1500 more than the 6-speed, so presumably they're keeping the latter as a lower-cost option. The quattro is only available with the 6-speed and the Sportback only gets the 1.8 with the 7-speed and no quattro option.