I use Nikwax down cleaner to safely clean down items. Never use detergent on down items. I read one person suggest that you should send it away to get a profession cleaning, but the whole point of this product is to allow you to safely do this in the comfort of your own home, and without the rather expensive cost involved in doing that. I have recently used this on a Rab Down Neutrino body warmer, a Rab Expedition Jacket, and a Rab 4 season down sleeping bag, and every item is now spotlessly clean, and the "loft" of the down has been restored to that of a new jacket/bag.
I use the bathtub with the solution of Nikwax down cleaner, and warm water to gently wash the item. You should rinse the items several times so that only clear water seeps from what you are cleaning. Then you can drain the water, and gently press the excess water out of the item. You can then spin dry on a low spin setting, and then lay flat to dry on a warm day, or place in a drier on a low heat setting until dry.
Yes it does take a couple of hours to do, but given that good down products are generally expensive, I don't mind putting the time and effort in. It really is possible to achieve the same results that professional cleaning achieves in the comfort of your own home.
Don't forget that a clean down jacket is a warm down jacket.