Thanks again Peter, will give it another go, probably being dense here but re the response graph which is the response trace, the darker upper one? In general terms what did you think of Fred's design? I attached both schematic and graph for easy quick glance. Fred Nachbaur died a few years ago unfortunately but some his work and design's are available here for those interested -
http://www.dogstar.dantimax.dk/tubestuf/index.htm
Andy.