Whilst the full amount of a PF doesn't have to be paid on the spot, an authorised collector can ask you to pay at least the original fare that was due.
I suspect it's the OP's inability to do this which has resulted in the situation escalating the way it has, though £250 seems excessive unless this isn't the first time.
I suspect it's the OP's inability to do this which has resulted in the situation escalating the way it has, though £250 seems excessive unless this isn't the first time.