Car appreciation... the aesthetics, the engineering, etc

It's a long time since I dealt with motor insurance, but adding a second car as a "temporary additional vehicle" is straightforward: the policy will be transferred to your new car and a cover note issued for your old one.

Obviously a common situation and this was the easiest way of dealing with it.

Cheaper than buying an independent, short-term policy as the premium has to be earned over a shorter period: if the car was totalled or nicked, the cost would be the same.

And test drivers relying on the "driving other cars" extension of their own insurance will likely have Third Party Only cover, so any prangs to your car won't be covered. You'd need to have them temporarily added to your policy for that.