Being cheeky I know. At Hollingworth Lake I had blownair heating. A One kilowatt oil filled radiator and a Maplin usb fan running over it worked brilliantly.
I had a 600 watt oil filled radiator and a 450 watt convector on at Hollingworth. I was cold. So I turned off the convector and used the onboard gas blown air instead. I left the oil one on to help it out a bit and hopefully save some gas.
In Halifax, I bought a fan heater like Molly3's. Much warmer, even when only on 750 watt.
I can vouch for how well Del's worked Carol, I think it may have been Bakewell club site when he first tried this, you couldn't really feel any heat from the oil filled radiator because its a PVC and as soon as you open the side door the inside air swaps with outside. I did not think a small fan behind the heater would really do anything and was surprised that I could feel the warmth as I was sat in drivers seat and the heater was just under the bed at the back. Well worth a try next time