An update to my earlier post, but first some background. I loaded the combination of Immunet and Bitdefender Free on one of my systems after reading the PC Security Channel's glowing report: I decided to exclude windows\temp from Immunet scanning on the basis that the Bitdefender engine would still cover it. The result is a much calmer system, albeit slightly less secure.
Bitdefender Free is a stripped down version with very few user choices. I cannot see a way to create exception/exclusion rules in Bitdefender Free. Bitdefender Free does flag up Immunet tmpscan in my rig which is a nuisance.