If no-one can offer a specific hotel try looking at http://www.hrs.de (let it load, change language to English and wait for it to reload before proceeding). They have a selection, the little coloured bars and scores are what previous customers thought (dark green is good, orange means run away!!). I know what you mean about time warps, although I usually get the 80's (the time when brown and orange bathrooms were fashionable!)

I'm not sure there has been a period when they were not in fashion in Germany! I'll try the site, thanks.