How can I make him get lost!?

I get the bus to and from school and I sit at the front with my sis monk and mates lizzie and amanda and we have done so for about 3 years.one day I got on the bus and a year 7 who acts like a year 11 was sitting in my seat and was dising me and my mates.lizzie,amanda and myself hate him becasue we cant talk to each other because he buts in and thinks its his buisness too and upsets my by insaling me music choice and autism.to us he has overstayed his welcome and he needs to get lost or sit somewhere else(thair is enuph space).lizzie,monk and amanda are year 11 and are leaving next term and I want to spend as much time with them before they go.but I cant when a unwelcome stranger is anoying us all off.how can I get him to get lost and sit somewhere else