Yeah, I have tried to find one of those too, so far without any luck. The problem is that they all stop at 14" or less, at least all those that I have seen. If you have heard about one with a 15.6" screen, please let me know! It doesn't matter where I have to import it from, money really isn't a problem, at least within reasonable limits, like £2000.
I was very close to buying a £1000 Dell Latitude XT3 with an i7 and 256 meg SSD, which would have been useful as a backup work computer as well since it fits the Dell docking stations that I have both at home and at my cabin, but that was 14" as well. I tried with my wife's Latitude 14", and it's a few centimeters too small. So I hope there is a 15,6" convertible laptop coming, or I'll end up with the very "secret" 18" all in one that Dell's supposedly coming with this spring.