Would euro solution be costly for Treasury?

[Gerald]

One of the more counter-intuitive predictions in the Office for Budget Responsibility's recent forecasts for the British economy was that the government would borrow £112bn more in the coming five years than it expected in March, but would shell out £22.2bn less than anticipated in interest payments.Or to put it another way, the OBR assumed that although the UK's public finances were deteriorating, so that that the national debt will be just shy of £1.5 trillion pounds in less than five years, investors would remain unprecedentedly keen to lend to the British Treasury.And on this scenario, borrowing costs for the British government would remain at or near historic lows.

http://www.bbc.co.uk/news/business-16028896

How plausible is this?

Note: 5 December 2011 Last updated at 08:22 GMT