DMC in Preston have one that was pre-registered in June (absolutely brand new) at a saving of approx £2500 I think.
Looking at one for 16K, 16 plate less than a 1000miles. From a non Ducati dealer though. Not that it makes a difference if still warranted.
My dealer told me there is no physical difference between a 2016 and 2017 XDiavel.... you will probably find that a lot of the bikes registered as 17 and 67 plates were actually manufactured in 2016 anyway.... I know my brand new bike was.