Since starting this thread I decided to try something new. When asking for the bill at the end of the meal I also ask if service/tip is included in the bill. If it is not then I ask for an appropriate tip to be added to the bill as a line item at the end before they bring it to me. So far 3 out of 4 restaurants obliged, the exception being a major pizza chain where the EPOS system wouldn't allow them to do it.