I've just had a 6' x 6' shed erected in the garden to house a few
stationary engines which I want to keep above freezing in the winter. I
do have an electrical supply nearby. What are folks thoughts on the most
efficient form of heating that will keep the shed just above freezing
point?.

Electrical Tubular heater 5' 200w (has the advantage of having a frostat
onboard)

Old fashioned paraffin heater (I would have to light it if the
temperature was liable to drop below freezing)

Any thoughts, comments or suggestions welcome