In reply to kate wels:
I've used Franklins OK. expensive but then these were PHD and Western Mountaineering Bags so its relative.
Have washed cheaper ones and only issue is potential damage to the internal baffles by the tumbling when the down is wet and heavy. So hand wash with proper down cleaner or pure liquid soap in a bath should avoid damage. After multiple rinses try to get as much water out as possible but without wringing it, then go to a Laundrette and use their biggest tumble dryer on low (arrange a bank loan since you will be there for a long time)