Unsweetened ice tea is a great flavorfull beverage with no calories and caffeine...
Admittedly, this is "Boozy Britain" though.
The 'I don't drink' part comes across to insecure people as judgemental or superior, so drop it.
They're not asking you for your convictions regarding alcohol / tobacco, they're asking you if want some / have a lighter they can use.
At any rate, you can answer why when they ask you why.
Despite their love of beer, I think that my health consciousness weighs on them... makes them feel a little guilty. Consequently, they make little comments about my lack of drinking. Harmless stuff, but my guess is that they're actually expressing disappointment in themselves.
I especially notice that when new people are with the group, the core members feel that they have to point out and explain that I only order water. So there's obviously some tension and discomfort there.
Totally disagree, nobody cares if you have 2 beers vs 8 beers.