The hat isn't from the Lux wedding, although it's very similar. The hat is from Ascot 2013.
The base of the hats are very similar that it makes me think it's the same base just different decor.
I love the hat as it's so Sophie and I also like the dress as the colours are beautiful. I just find it odd that everyone else, including her own husband, are wearing coats and she isn't. Maybe the dress is super warm!
On a side note I LOVED the outfit she wore to the Lux wedding - I loved that dress and those shoes need to be in my wardrobe now.