we're a funny lot cos i bet we have tipped even when it hasnt been deserved.
take valentines day as an example, i had to go through 3 knives to get a clean one in pizza hut, the waiter was bothering us every 2 minutes asking if we wanted a drink when we still had one, the meal was astronomically priced, yet we still left a tip!
when we went out to a restaurant they kept trying to make off with my bread roll TWICE and i had to say please will you just leave it - yet again we tipped!
we usually just make it up to the next £ or if say it was £28.50 we would take it up to £30, and no more cos afterall and i'm sorry, they are getting paid to do a job and most people dont get paid twice.