We have a UK grey outlet thats a genuine bricks and mortar unit,they have a 100% solid reputation for customer service and all there camera body sales come with a three year warranty,thats got to be better than buying secondhand from the likes of ebay,just an example.
Nikon D610 Body
What a lot of people forget is its the same camera your buying grey or official you only need to be certain of the back up,will i use grey well most likely not as i like to be able to take my problems back to my local dealer and hand them over.