Brits are saying 'thank you' less these days, according to a survey carried out by the TV channel Food Network. It's not that they are getting ruder, but that they are opting for more casual expressions of thanks - ta, merci, and particularly cheers. One synonym that the Food Network didn't mention, and that I know I say a lot, is 'lovely', although I may accompany it with 'thanks'. Dictionaries tend not to define 'lovely' as a word of gratitude, although I notice that the Longman Online Dictionary says about the word "used to show that you are pleased with something". I hear the guard on the train repeating 'lovely, lovely, lovely' as he passes through the carriage checking tickets. I'm pretty sure that that is meant to be an alternative to 'thank you', rather than him being particularly pleased at the sight of train tickets.