Hello Jamie - sounds like you're now back on your feet after an awful summer.
What about doing it yourself using one of the disinfecting products which are used to stop nasties growing inside rebreathers? After all, this is sold for use with with diving equipment. There would be a cost involved in obtaining such a product but probably a lot cheaper than if you "have it cleaned".
There's plenty of rebreather pilots in the CDG, who could probably advise further.