I think it's a 'lot of hot air'. Did I hear the chap say at the end of the video "8p per day, plus electricity".? I counted five lamps in his small office. Possibly more heat from the lamps and computer than the flowerpot arrangement.
My favourite from the comments on your link Sandy...
"Apparently, EDF have bought out all the candle factories, and are now putting the price of those little tea lights up to £8 each, not least of all to cover green taxes, stealth taxes and the Tory Christmas party fund tax.
The price of flower pots is expected to rise soon as well..."
Just remember that some plastic flower pots are made to look like ceramic pots. Lidl are selling packs of 50 Tealights for only €2.5 (in France) so now you can heat your house for even less (than a lot).
An even cheaper way to heat your house is to burn old chip oil in a baking tray using old socks as a wick. If you haven't any old chip oil, I've heard that wood burns quite well and isn't expensive.
@jomifl....Sorry, I am lost by all your costings. Your latest is £0.03.... Per hundred, per tealight or is it just 'perhaps me'.... which should be extinguished.? A hot question for you to answer.:-)