I got a set from ebay (will post the link when I find it), they are GM dealers who sell stuff on ebay. Anyway, the wipers were about £20 including delivery which is about the same as Halfords charge for regular ones.
I can confirm they are the best I have ever had. They do not lift at speed (not that I've been that fast to test them, AHEM) and always wipe clear, though as mentioned above they are brand new.
My only complaint and it's something I can deal with, is the massive white GM logo on each blade that distracts you whilst driving. I'm going to get a Black permanent marker on that. if that fails I'll paint it.
They do look a little odd from the front, but other than that, absolutely fabulous!
Bri