I was pulled out of purgatory and back to the counter.
Seatbelt extensions had been found and apparently prepared for both legs of the flight.
The new cabin bag ticket was likely (although not guaranteed) to be cheaper than the original ticket purchased, so reimbursement should not be an issue.
I handed over my credit card.
And went and bought an emergency bag of crisps and bottle of water.
Gin might have been more appropriate.