Minor point about Crewkerne - line between Waterloo and Exeter is now open again
HMRC absolutely hate the idea of any sort of suspension of tax in any circumstance - mainly because they are terrified that once they make a clear public exception in one place, then people start making claims that taxes should be suspended elsewhere. The only reason HMRC give way, is when a High Court judge tells them to do so - and a big court case will take much longer than the time it takes to repair the line at Dawlish.
For this reason, unless the Chancellor issues an explicit order, I doubt anything is going to happen on APD suspension.
Yes, people in Cornwall are genuinely being given pain, but some of what's being said by politicians is added political spin. Business and day-to-day affairs are being hit hard, but talking about the impact on tourism to an area which emphasies its rural nature in February is less than clear cut.