Yes, I think it's the balanced bitterness of the hops that somehow cuts through the physical and mental thirst. Challenging but soothing your sense of taste. Overly hoppy American-style IPAs don't do the job, because it's all bitterness. Similarly Caribbean malt drinks, that have the malty sweetness (obvs) of beer but without the hoppy bitterness are just cloying.

Ice cold tonic water with freshly squeezed lime will sometimes do for me in a similar way to your iced tea. I'm intrigued (or more horrified) by this 0.0% gin they are now peddling (for practically the same cost as regular gin despite the complete absence of duty). Surely the 'alcohol-free G&T' has already been invented, in the form of just the tonic water. I guess you could crush some juniper berries up if you wanted, and job done.

Is Pelforth the one with the pelican logo/mascot? That seems to ring a distant bell.

Cheers!