I know they appear on Classic fm tv and also do a version of "with or without you", can't find them through google or on the classicfmtv website. You might want to try submitting your query with classic fm through their website at www.classicfm.com sorry I can't be more help.
There's a Belgian choir called Scala, who have an album called 'Scala on the Rocks', where they cover Smells Like Teen Spirit, as well as various other rock songs. Not sure if they're the one you're after. Their website is http://www.kolacny.com/contentv2_frameset.asp?language=E NG