My wife and I regularly do house swaps for the whole summer. This year we are off to the States and as part of the deal we are swapping cars. However, our insurer would not add the American visitors to our policy for the required four weeks. We had to swap insurers to Aviva who, for an extra £160, will insure the two Americans for 32 days.The Aviva policy is about £150 more expensive than my current one so the exercise is costing £300 in insurance alone.