I tend not to tip in the UK, but do occasionally if I’ve received good service. When I say service, I mean the sever, as I see this separate from the quality of the food.
On my visits to Japan, I don’t tip. If you ever get the opportunity to go there, don’t tip. They generally find it offensive, from what I’ve seen.
When I’m in the US I tip 20%. In a way, to me, it seems somewhat expected. Even to the point of a taxi driver counting the money I’ve given him, 3 times in front of me, as though he was are looking where the tip was.
One time in the US, I was in a restaurant with a friend – he had been deaf from birth. The woman server had some difficulty understanding my friend, and wrongly put it down a strong British accent. Later, the server negotiated with another server to serve our table. Who then served us for the rest of the evening. It was my last day in the US, and we were shortly to head off to the airport. My tip was to empty my pockets of US money, which was considerably, and leave it for the 2nd server. Who collected the tip from the table and waved it to our first server. So good for him, I thought.