You could try this company to have them proffessionally cleaned, W.E.Franklin (Sheffield) Ltd, +44 (0) 114 268 6161
http://www.franklinsgroup.co.uk
The only company recommended by Rab or this is how they say to do it yourself;
RAB down products can be home cleaned, however this is a difficult and time consuming job.
Please give it careful consideration before starting
Washing items yourself.
•Carefully hand-wash the item in warm water
(40°C) with a soap solution, NOT DETERGENT.
•Rinse thoroughly, making sure there is no soap residue present within the product.
•Squeeze out all excess water gently with your hands and transfer item with care to a washing machine. A delicate ‘spin’ programme is recommended.
•If you are cleaning a box walled garment or sleeping bag, ensure that the weight of the item is supported by ‘cradling’ in a bath towel or similar. Failure to do so may result in damage to the down compartments.
•Immediate tumble drying should commence in a commercial dryer on a ‘cool’ setting. Check the item periodically and repeatedly turn inside out. The down contained within the baffling may require further manipulation in order to restore the loft.
•Avoid the temptation to remove the item from the dryer too soon. Although the outer fabrics may feel dry and warm to the touch; down contained within the baffling can still be clumped because of moisture.
•The drying process can take several hours. When finished it is advisable to store uncompressed in a dry, cool place.
•Airing should continue for two days before use.