Because its on a 6amp mcb with other stuff running of the same mcb as well. My garage is detached and the cable running to it is buried and would need upgrading if i wanted 16amp going out to it. Its something i intend to upgrade at some point but not at the moment as its a bit of a job.
OK. So my guess it that it has been taken off the main socket circuit of the hose as a spur. Best way to check is if the house fuse box has a seperate fuse for the Garage.
Do you own the house and if so, when did you buy it?
We bought our 60's built house 12 years ago and had to make upgrades to the electric before they would grant us a mortgage (earth wire to lighting circuits and RCD onto garage supply. We also had to remove the wiring to the outside lights as the wiring was not amoured type.
If I were you I would try to fit a 13 amp spur from the house onto an outside house wall using a weather proof socket and run an extention from there to keep you van from freezing. Freezing damages equipment and can prove to be very costly if this happens.
Personally, this would be a priority.
We live on the North East coast and use an 800 watt modified wall heater in each of our vans with a frost thermostat. Its kept us going through the terrible winter of 2 years ago without issue.
http://www.ebay.co.uk/itm/CREDA-SLIMLINE-PANEL-CONVECTOR-HEATER-1200W-WALL-MOUNT-ELECTRIC-HEATER-BNIB-/320934125866?pt=UK_Home_Garden_Hearing_Cooling_Air&hash=item4ab92a212aThey look similar to this, but I welded up a frame to mount them on. They must be at least 30 years old. I got them off a skip on my way home from work 22 years ago when I lived in Johannesburg, and they were old then.