Barton,
With short term car insurance, age is a very important factor. There are just around 8 companies which provide temporary car insurance and just about 2 which will insure under 23 year olds. Since your son is just 22, you're limited to these 2 companies and if they decide not to provide cover for him for whatever reason, then you're stuck. The only other thing you can do is instead of getting 15 days car insurance is to get a whole month's worth of cover with eCar Pay As You Go Insurance. After a month, you can either cancel or renew it.
