There isn’t. But I doubt anyone has much stomach for bloodshed, fiscal or otherwise.
That depends on how much potential cash is tied up in the issue. If enough money is involved, they’ll find a ‘moral’ reason stop the UK, with force if necessary.
One of the reasons for the Civil War here was the South’s plan for a 10% tariff, combined with its control of the mouth of the Mississippi. The Yankees saw visions of empty ports and grass growing in the streets of New York and Boston - there was no choice but to go to war...