That seems to have worked. I hung the hose in a U-shape over the
bath, filled it with bleach & cold water (it stretched out quite a bit
in filling, so I think I got all the accordion-like folds), left it
overnight, rinsed it out with cold then hot water, hung it up
vertically for a couple of hours, stretched it out (with help) & blew
the hair dryer through it for a few minutes, then hung it up
vertically in the airing cupboard overnight. It smells OK now.
A lot of fuss & I've learned not to get it wet again!