Sorry, I should have said, I have lived in Canada for several years now, so am familiar with the North American tipping culture. The 0 and bad service on the credit card line is an American btw, in the UK they use chip and pin almost exclusively so there isn't that option.
The culture is different, but the job is pretty much identical which is why I don't feel tipping for poor service helps anyone (except the rubbish servers). Even with me, and a couple of other people refusing to tip for bad service, that guy is probably still making more an hour than the people who give excellent service in the UK. For the same job. In very similar living conditions (I am not going to try and compare the US and a third world country server).
I have to say, in Canada, I understand it even less, because the servers are paid, almost exactly, the same as British servers, and then Canadians get the tip on top - it is lucrative being a server in Canada from what I have witnessed - and I see that in the demographics - in the UK a huge number of those working in bars and restaurants are under 25 - it is probably the most normal job to hold when you are finishing high school or at Uni - I think most of my friends did a stint as a bartender, server or catering waiter while they were in high school or Uni. In Canada I see far more people over 25 employed in the industry, I guess, because it is a lot easier to make a good living here by doing it.
In the UK minimum wage is pretty similar in its purpose to the US minimum wage - it is what the government deems is enough to live on when you work a regular working week. It is based on things like cost of living, rate of inflation etc. At current exchange rates, it is around $9 US an hour, and then you pay tax, national insurance etc. on that. The cost of living in the UK is higher than in the US (for example, I will compare apples with apples, London and New York say, London has a far higher cost of living than New York) so in real terms, servers in the UK do not actually get $1.75 more, as their costs are higher too. The majority of UK workers in the restaurant industry would not get things like pension, private health cover etc.
I agree there is no excuse for bad manners on either side!