Thanks for the replies, I am working though your suggestions.
To dhenry I considered this when first designing the project I like the PID to limit the power to the element on start up the library allows to set upper limit this allows me to get the viscous liquid warm so as not to scorch and give off flavours, but it is the easiest solution so may risk the scorch to get the light steady.
The lights are ling tube with electronic ballast.
Incandescent bulbs do not flicker.