Same, I only know one or two British people who don't drink Coffee, I don't think its considered an "american" drink at all.
When I said 'American' drink, I meant that's more what the Americans are known for... having better/more coffee than the Brits. Yes, coffee is available everywhere in the UK, but it's mostly instant (at least the stuff you buy in the supermarket, not necessarily what you'd get in a coffee shop) and from what I understand, instant coffee isn't too favourable compared to the ground stuff.
In terms of whether you would find coffee on a British food shop site, I'd say it wouldn't be something that would be stocked because British expats in the US will be surrounded by a wide variety of coffee, so they aren't going to need to import it from the UK.
unfortunately, i'd say the best of british food is stuff you can't get online--fresh produce & cheeses.
Yeah, that's my issue - the things that I miss most from the UK are the fresh/dairy products that you cannot bring through customs - I miss my English cheddar, Double Gloucester with Chives (although I have found this once or twice in Kroger/Smiths here), double and clotted cream, milk etc. I also miss Kingsmill bread - which, although I could get it through customs, it would go stale before I had a chance to eat it!