Aye timbo and SteveL,
I have an old Carron 'Tortoise' stove lined with fireclay in the workshop, but I do like these stoves and have seen a double barrel version consuming half pallets, with the upper barrel a nice cherry colour!

However, I'm not to sure about using a 'clip top' barrel as per the illustration. I think a whole barrel would be better.
As for the bottom of the barrel, to prevent it burning out, a layer of flat 2.5cm firebricks with another lying up the side of the barrel on each side and a layer of playpit sand to blind it all will do the job nicely. The stove in the house has a 1" - 2" layer of sand on the bottom to start the season off and then you just need to remove maybe a shovel of ash a week to keep the level down a bit.
There is also one of these with the addition of a waste oil drip feed into it, but I can't find the link!

Keep toasty!
My regards, Bill