Cunt is possibly the worst thing you can call someone in the UK but it generally doesn't offend anyone. As for see you next Tuesday, it's used ironically as a way of getting a laugh. So you'll say see you next Tuesday and people will get the gist of what you're saying and find it funny. Using see you next Tuesday as an insult is long winded so it's easier to just call someone a cunt, though you can use it as a descriptive to remain courteous, so for example "and then I called him a see you next Tuesday and walked off". Thus ends your lesson in Cuntology.