This gown actually looks very beautiful & figure-flattering on Catherine in the pics I saw. I like the pearls on the stomacher, & the fur sleeves. In a sense, the dress is accurate in one respect that Catherine dressed in black a lot in her later years, probably to mourn the six other children she lost in her tries with attempting to conceive with Henry. She was very dedicated to her faith as a Catholic, which probably bored the boisterous and flamboyant Henry later in their marriage.
Hehe, I read a quote on the Tudors Wiki somewhere that one girl wrote "I remember wearing Tudor-era costumes. They were always so warm below & freezing on top."
Although the real Catherine would have never worn anything with that low of a neckline. From what my mother's told me, she was a modest lady. (My mother loves reading Tudor history & Elizabeth I). The gown might have been more accurate with a linen under-collar & a gable-hood headdress, but from what I've seen, it looks as if Joan Bergin took a look at those things & said, "Let's just throw it all out & play dress-up."