Swindon to LHR...
I had a train ticket from Bath to LHR, but First Great Western decided to replace that service with a coach between Bath and Swindon so they could do engineering work on the track.
They cunningly allowed the connecting service to depart before the (delayed) coach service from Bath/Bristol could arrive. Then the next train was going to be sufficiently late for me to miss my checkin window at LHR.
After a shouting match with the station manager (who wanted me to go to Reading, and get a taxi from there ... only that would leave about 20 minutes for the journey, yeah, right), they finally wrote a taxi warrant for me.
I dread to think what that cost, in a black cab and on the meter.