Another option for a future build is the Propex line of forced air propane furnace. These are similar in concept to the diesel heaters but obviously run on propane.
Propane as a heating fuel has some advantages over diesel: No noisy and unreliable pump needed, the odors during normal use are minimal, consistent fuel quality, no fuel gelling problems, long term storage does not affect fuel quality, and a big one: No road taxes are imposed or paid. (there might be some exceptions in some places)
Similar in cost to the Webasto/Airtronic/Espar line, the Propex heaters are designed for permanent installation.