Hi Eddie
I carry a 2KW fan heater which heats the van up very quickly. It also has a setting for 1KW and an option as a cooler. They're fine. Only downside is I find them to be quite noisy.
I use a halogen heater in the awning for the dogs when they are in their crates. I site the halogen heater in a suitable place, and adhere to safety issues etc. I like the halogen heaters because if you knock them slightly or knock them over, they will automatically switch off. Only downside with a halogen is they are so bright, if sited opposite, they blind you!
Fan heaters circulate the heat around an enclosed area nicely, although they take a while to do that. I find that halogen heaters are better for directional heat in an awning for instance, but they will heat up a van nicely too. My halogen oscillates.
You need to bear in mind that both the fan and halogen heaters will draw quite a bit of electricity if used on the full settings.
Lisa