my folks brought me back some yerbermate tea from argentina so hopefully I will finally find a tea that matches my requirements.
Yerba mate is a cultural icon that should be far more widespread than it is.
The caffeine content is substantial but the other chemicals supposedly counteract some of caffeine's less pleasant side effects, like increased heart rate and "the jitters," as 1950s ads for decaf Folgers crystals terms it.
Do you have a proper mate cup and bombilla? It really is not the same in a tea ball.
Pedro has been drinking yerba for years and it is wonderful. A tip: if you like strong tea it should be right up your alley, but if it's too bitter for your British palate you might consider adding a pinch of sugar to the yerba before you add hot water. It brings out the minty sweetness of the leaf and makes it go down a bit smoother. (I always drink mine with sugar, even though I like very strong tea. I can drink it without, but it's pleasanter with, IMHO.)
Also, my brother-in-law swears by the technique of shaking the cup vigorously to make the leaf powder rise to the top. Then he half-fills the gourd with cold water and tops it off with near-boiling, which he says makes the tea less bitter because straight-on hot water will burn the leaf. But Pedro just dumps the leaf into his gourd and pours boiling water on top, and nearly always singes his tongue when he takes his first sip.
That's how Chuck Norris would drink mate.