I used to have some golden necked d'Uccles. I only had a few.
They are friendly, wonderful chickens. They are hawk bait, and aren't very cold hardy. Additionally, the hens are so very small that I wouldn't recommend having them in with large fowl roosters.
I noticed two "styles" of my GNs that I bought from Welp Hatchery (I would order from them again...they were great!). Some of my GNs were very light...almost all white with golden markings, and other ones were almost all golden with some white. I loved them both.
I am no genetics expert and I am only replying to tell you what I found in my experience.
We are switching back to large fowl as we have so many hawks and we want the larger eggs again. This is a breed/color that I would love to have again later on.