That's already happened where I live, the village petrol station has closed, leaving the nearest petrol stations as Tywyn (10 miles) or Dolgellau (8 miles). To get to Barmouth's petrol pumps is a 40 mile round trip despite being just a couple of miles across the estuary.
Driving in rural areas takes a lot of planning and forward thinking, something which regularly catches out visitors to the area more used to having petrol virtually on tap.
Coming back to Hydrogen trains, I can see there being potential for hydrogen fuel on something like my local line, the Cambrian. We have a windy coastal location, and a wind farm plus sea water gives the potential for hydrogen generation, although with Cardigan Bay being a special area of conservation interest putting windmills at sea might be an issue. However, there must be a point coming soon when the combination of coastal waters and wind potential must make the hydrogen option more cost effective than it is at the moment, unless battery power really takes off.
This is actually a factor in favour of electrification. At absolute minimum, it should be possible to provide a 3 or 7kW charger using a standard domestic power supply. A trickle charge isn't great if you need to fill up during a journey but it would work fine for someone living there who leaves the car parked at home or work for a good portion of the day.
While rural electricity supplies might not be strong enough today for rapid charging, that doesn't mean it'll always be the case. Until recently, rural areas would have had electricity for lighting and appliances but many people will have still relied on fuel for heating and hot water. Combined with the way that their vehicles were powered by petrol or diesel, there wasn't much need to beef up the power supply connections. That's changing now. For one, rural areas are the ones where you've normally got the most ready supply of renewable power. The wires to bring power from a centralised power station to remote rural communities can also be the ones to take power from near those communities and feed it back to the larger urban areas. Micro-renewables mean these connection upgrades will filter down to the level where you can think about connecting up heating and EVs.
Some of the largest institutional supporters of EV rollouts have been electricity companies. That's not surprising if your business is selling electricity - the more EVs there are, the more electricity needs sold. The economics are very much in favour of it because the incremental cost of moving more power by electricity isn't that great. The need to get a critical mass of electricity use was why electric supply seemed to replace coal(gas) for heating until natural gas came about. With natural gas going out of favour, and major improvements to efficiency with things like heat pumps, we'll see that shift back to mass electricity use.
So, what we might well end up with is a position where grid supplies become available in rural areas which aren't available today. Sure, you might not have a substation sitting waiting at Corrour any time soon but you may well have a good supply of electricity in villages like Crianlarich. An electric train charging rapidly won't be as much of a burden for a local grid designed for 100% electric heating.
The consequence of all this being that the niche that hydrogen trains can fill, even in more rural areas, gets narrower still.