In reply to haydn: That will be fine. Even if you used detergant it would only strip the reppelant coating not damage the membrane (actually there is some argument for using detergent to get them really clean, followed by pure soap to get rid of the detergant). Either way you'll just need to go over the surface with a replacement coating (probs nikwax) once they are dry (or nearly dry depending on manufactorors instructions). Make sure you don't dry them in a really hot place, under a radiator etc.
If they are natural leathers/seudes may I recomend nikwax aqueous wax, recomended to me as "the mutts nuts" last year and I have found no reason to disagree.
Hope that helps and I'm not just spouting nonsense (I'm good at that).
