Ok, so first google hit has some good practical examples that cover this well:
Frustrated Contracts | Law | tutor2u
And the second hit with much more detail:
Frustration of Contract: Law, Discharge & Consequences | Solicitors London
Some key takeaways for me:
- A force majeure clause, provided it is written properly, is likely to take precedence. So, it would seem a 'no refunds' clause supersedes contract frustration. Or, as I suggested above, makes the cancellation a defined part of the contract.
- "A contract isn’t frustrated just because it’s become more difficult or expensive to perform." So, if the airlines are shut down one could still rent a sailboat.
- "If some sort of pre-payment or deposit has been made, the buyer can get that pre-payment back, minus any expenses incurred by the seller." - a 1 for 1 credit for a later trip would not be appropriate as the vendor would have incurred some costs on the cancelled trip no matter what (they might be only administrative or they might be more).