What if something can't compete? "viability" vs "competitiveness"

Chemical companies use oil as a feedstock to make plastics, glues, etc because it is still cheaper than alternatives. British coal has mostly been replaced by cheaper imports. Won't migration to alternatives raise prices and lower living standards?

Yes, but how much? There is a basic paradigm that's useful here: "viability" vs "competitiveness". In most industries a very small cost difference can make you uncompetitive. That means that slightly higher cost solutions will be avoided, which can give the impression that those solutions are higher cost than they are. OTOH, if changes in the business environment (or natural environment!) change the costs of alternatives for everyone, suddenly alternatives can become acceptable in that industry.

There is an analogy in sports: "winner takes all". Tiger Woods and Pete Sampras get all of the publicity and a lion's share of the prize money. The 200th best player in either sport gets no publicity or prize money. On the other hand, the 200th best player will mop the field/court with you or me just as fast as would Tiger or Pete.

So, for instance, recycled materials are in general slightly more expensive than virgin materials, plastic included. But, if oil becomes more expensive then recycled materials could suddenly become the standard. If something could be recycled with only 10% loss at each generation, that would reduce the consumption of virgin materials by 90%, with only a very small additional cost for the industry.

As another example, high sulfur Illinois Basin coal costs perhaps 2 cents per kWh to scrub. That's an enormous margin to power plant consumers, who are willing to pay for long-distance transport of lower-quality Powder-River coal. The net difference in cost might be only half of one penny per kWh, which is still an enormous margin to power plant consumers. On the other hand, let's assume power prices rise by one half penny around the globe (to eliminate questions of regional competition) - how much difference would it make to consumers to add a half penny per kWh? Sure, they'd notice it, but would the difference cause any factories to close their doors, or homeowners to not be able to pay their mortgages? No.