Oh, and search the past threads. Tipping comes up regularly on UKY. Some in a nutshell stuff--tip waiters at restaurants where they take your order at the table, but tips aren't generally nearly as big as the US ones. You can tip a bar keep if you want, but what they will often do is say they can give themselves a drink as well. They can't drink on shift, so they'll add a drinks' cost to the bill and have a tab for themselves when they aren't on duty.
In my area, it's kind of up to you if you tip for things like food delivery. I usually give a small tip to the pizza guy or the Chinese delivery--especially if it's a cold night and the food was on time, but in our area, I don't get the feeling it is expected at all. I think a lot of delivery drivers for big companies like the Tesco deliveries, aren't allowed to accept tips. I'm pretty sure DH gave a nice tip to the mover when we moved house though.
I usually round up a taxi fare, but I've heard some argue to not. I've been told that it was the tradition for bin men and postmen to come around with a card or something at Christmas/Boxing Day, and you'd generally give them a tip for their work during the year, but this hasn't happened to me yet. Even our posties who come to the door disappear so fast, we don't get to see them much if at all.
The one I still can't get my head around is tipping Christmas carollers. That is just odd!