Well I enjoy taking the p**s, but as an older person, I also know that I couldn't travel much further than Bristol to Exeter without needing to use the loo, and know the same applies to many others of my age. I would be interested to know what would happen if I had had an advance ticket for that service, and had either chosen to travel on a later service because of its lack of toilets, or had used it but got out at Exeter and then caught a later one for the same reason.
I would like to think and I'm sure
GWR▸ would make an exception in this situation because they were unable to provide a train with the usual facilities.