It is still mentioned in the CAA CAP 413 radiotelephony manual in the index in chapter 1, page 8:
http://www.caa.co.uk/docs/33/CAP413.pdf
The definition is like Billiebob said. I heard someone say a while ago that it is used on some high elevation airports in the world. Does anyone know how exactly? Would be interesting.
Wikipedia also has the wrong definition of QNE, but they mention QSY and QFU. I think only the last one may appear in some official publications, but not in the UK I think.
regards,