I am with you guys on the teabag thing although I don't think it's really a "British" thing; if Americans drank as much tea as Brits did, we'd probably have our own proportionate number of teabag hoarders.
My inlaws use one of those savoury pie dishes (the ones you'd make a single serving dish of say steak pie in) to plop their teabags. They NEVER empty it, and it piles up. I empty it when I see it towering (and I only drink about a cup of black tea a day). They must have the impression that I like to empty it because after that, they would always leave it for me. Then if someone is washing dishes, they will empty old teas into the dish as well, usually without emptying the teabags. It's so friggen gross. Plus, even when they do empty it, they don't wash it, so it's all grotty. I like to use a small saucer to make the tea and use to take the teabag to the rubbish without dripping. I am not sure what's wrong with throwing them away wet, but I always wondered what was up with the wet teabag collection. I might leave a teabag in the saucer if I am in a hurry to bring tea to Mr. A, but I never leave it long. Ugh.
I could probably fill a few posts with inlaw gross out stuff (like leaving raisins for their crap factories chinchillas which the chinnies then push out of the cage, onto the floor, which rolls up with any poo that happens to fall out at the same time, and gets stuck on passing feet), but I won't.