These new S class PE fares are fantastic. I was able to get a Xmas SFO-LHR-SFO for $1300, and best of all, was able to upgrade to UC with miles on the spot. Last year I ended up paying slightly less for a non-upgradeable (at least not anywhere but at the airport on the day, if you're lucky) K class fare.
Does sound like a good deal. I always used to buy K fares, but if the S fares aren't that much more and you can confirm an UC seat at the same time, that sounds like a no-brainer.
Pix