That is not the problem, but thanks for the info.
I have another simple example.
Please note, R1 in the picture has been changed to 1k for 12v and 330R for 5v on the actual simulation.
Battery B1 at 12v, switch works and transistor switches on LED.
Battery B1 at 5v, switch "works" i.e. changes state, but transistor does not switch LED, take transistor out of line, and connect LED to switch direct, works fine.
I'm sure there must be a setting in Proteus for the transistor but I just cant find where it is.
Any help?