I haven't read through all the responses but my solution is
www.nuu-muu.com. UK distributor:
www.tunix.co.uk (selection usually limited to just the current releases). Layer up, layer down. Covers your bum, doesn't snag on saddle (YMMV but mine are Selle SMPs with the "eagle nose" so this is an important point). Washes in the sink, dries in a few hours. Doesn't smell. Pretty as heck. Prepare yourself for lots of compliments and "where did you get that cute dress?"