Thanks for the quick reply but alas that doesn't work, that seems to break the objects up into lots of individual poly objects ballooning the scene size, and also quite a few of them, all individuals. They are set to match the forest item display parameters which as you can see in my attached image thins them out quite a lot!!
Maybe I need to do an uninstall / reinstall and put them all to the shared directory option?
Also I am now getting the vertical wall presets not rendering, also doing this randomly, it's rendering the vines but no ferns, I'm guessing re-installs needed. No point wasting more time.
I'll try using the shared directory structure this time.
I've rendered many times before with forest pack with none of these issues.