I have a king size duvet, bought in France. The label states the size as 220 x 240. Why is is that when I buy a UK king size duvet cover, its size being given as 220 x 230, I have about a 25 cm spare material overhanging the side of the duvet??
Is it as simple as ... 'your duvet cover is 10cm bigger than described and your duvet is 25cm smaller than the cover' ... what exactly is the 'question'?
Could you take it in on the longer end? If the excess is on the length eg from top to bottom, take it in at the top. If it's at the side take in equal amounts from each side. Problem solved!
This is normal: in France king size beds are 200cm long rather than the norm. of 190cm. If you have any material hanging over a duvet it's just because of shrinkage at the first wash.