What if I had paid £5 for a seat reservation (which, according to some on here, some TOC's do charge) which I suddenly lost because the reservation system failed? Would this realistically be deemed fair?
You've not paid £5 for a seat reservation, so this is irrelevent. Even if you had, your problem is with the TOC. The TOC has failed to reserve you a seat. You don't have a reserved seat - this is an issue for the TOC not the person sat in an unreserved seat which was supposed to be, but was not, allocated to you.
