I don't think he says "I need a new fun fair", I hear the lyrics "I need a new f***friend" instead. So yeah, it's about a cheap sex-based relationship and what I think is that the guy wants to leave because he thought that this f-friendship was going to be something more, yet the girl moved on to another dude whilst still not kinda have completely broken up with the lead yet. And at the end he says "I guarantee you will miss me" as a way of still coping with the fact that he wanted a long term commitment from a f-friend.
I don't think he says "I need a new fun fair", I hear the lyrics "I need a new f***friend" instead. So yeah, it's about a cheap sex-based relationship and what I think is that the guy wants to leave because he thought that this f-friendship was going to be something more, yet the girl moved on to another dude whilst still not kinda have completely broken up with the lead yet. And at the end he says "I guarantee you will miss me" as a way of still coping with the fact that he wanted a long term commitment from a f-friend.