Actually it rises to about -50V when I let things warm up.
I am thinking it may be one of the EL86 tubes. I was assuming warmth meant it was probably glowing but now I have taken the shields off I notice only one glows an nice orange and the other one flickers and glows purple/pink. I notice the purple/pink glowing one has some soot/burn marks inside the glass. Photos attached..
Anyone down under in New South Wales have a tube tester :)?