I can only illustrate this for a typical UK insurance policy (which you probably wouldn't be able to buy as a non-UK citizen) but don't think it's a good investment. Anyway, you need to add the excess to the cost of the policy then double that to account for the fact there's two of you travelling.

Only if a claim is going to exceed that figure is it worth you insuring against this one fact.

Working on the excess being £30 and the premium being £15, you'd have to spend at least £90 on a claim to make this worth your while.

There's also the risk that the insurance company may dispute your claim (i.e. if you get a cab to Glasgow and stay in the Hilton) that should be incorproated into any calculation.

I see there's a travelodge on the outskirts of Ayr - it only opens on Dec 15th so would be in good condition and they have rooms (non-refundable) for £26 a night on Dec 30th. Obviously you need to factor in getting there from the airport, but this would seem like a better insurance policy to me.