In reply to Babika:
I have two "Daimor Monch" down bags bought in 1980. Both are still in use, but are 2 season rather than the 3-4 season bags they were when new!
I've washed them by hand several times over the years (never risked a machine) but both the washing and the drying were such a faff, even with a tumble dryer. Hours in the dryer on low, and even with two tennis balls in there I still needed to spend a long time "unclumping" the down through by hand.
I thought I'd check out commercial cleaners and if the price isn't too steep, pay for someone else to take on the hassle!