If I have booked a ticket from x to y, I do not care which operator I have booked it with; I want to get from x to y... [If] I'm not on my booked train through no fault of my own, and when there are perfectly good trains travelling along the route, I expect to be allowed to use those other trains... UK rail needs to be seen as a national network, from the passenger's perspective, not a group of separate railways.
And so you can! By returning your cheaper Hull Trains ticket to Hull Trains for a full refund, and buying a new ticket that is valid with LNER.
If the UK rail network was fully integrated rather than run by separate train operators, your cheaper Hull Trains ticket wouldn't exist to begin with.
Seems odd that LNER don’t have enough capacity to offer ticket acceptance today but will find space for you if you buy a new ticket at £100+ as per HT’s instructions.
They might have the capacity to carry the five people expected to purchase the £100 fare while not having the capacity to carry 200 people holding £20 fares.
Moreover, this is not solely a question of capacity. Virgin Trains (West Coast) has plenty of spare capacity on late evening arrivals into Euston but, although Virgin assists LNR during infrastructure problems (and LNR reciprocates), Virgin doesn't exist as a free back-up for LNR passengers when LNR cancels services due to threadbare staffing levels. It might be possible to *physically* accommodate all displaced LNR passengers on late evening Virgin arrivals into Euston, but Virgin offers a premium service with premium fares - a premium which would disappear if Virgin services were swamped with LNR passengers paying a fraction of Virgin's own customers.
The prior knowledge of Hull Trains' customers about Hull Trains' reliability is irrelevant. Hull Trains customers holding cheaper "Hull Trains Only" tickets (some will hold "Any Permitted" tickets) limited themselves to Hull Trains services of their own volition. Once aware that Hull Trains services are disrupted, these customers have the choice of accepting the alternative transport offered by Hull Trains, or requesting a full refund from Hull Trains and buying a new ticket valid with LNER. This approach is fair and standard practice in any industry with competing businesses.
According to Hull Trains JourneyCheck, Hull Trains are today offering to reimburse passengers the cost of alternative LNER tickets, because Hull Trains are unable to source sufficient road transport. This is a fair outcome for Hull Trains customers. Also, if all Hull Trains customers use LNER over replacement road transport, swamping LNER services, this doesn't devalue LNER's offering because all displaced Hull Trains customers are paying just as much as other LNER customers.
While I understand that this isn’t LNER’s issue it doesn’t show the industry as a whole in a great light when different companies don’t work together for the good of the passenger.
While analogies are regularly misused by rail staff, I think a fair comparison in this situation would be expecting department stores such as John Lewis to accept Debenhams gift cards because Debenhams doesn't have the stock to fulfil orders. The only store sustaining reputational damage here is Debenhams, not the rest of the department store industry for refusing to "co-operate".