Ant's... Well, Amdro has always been the natural solution. Although officially it's for fire ants, and I'm not quite sure if it's sold in Her Majesty's land.
I've heard mixed results about compusive measures like gasoline, oil, etc. If it doesn't work, surely you're doing something to the earth.
Generally, an ant nest is 10 times deeper than it is wide, and the Queen is (if I remember correctly) 2/3 of the way down. If you can find anything to wreak havoc that far below the earth, that should do it.
Failing that, ask the Royal Navy for a bombardment, or me for a good Texas-chili-bomb run!
