Is there such thing as short-term insurance in the UK? Like if I wanted to insure a car for 7 days?

I am toying with the idea of buying a car in the UK and driving it during the meet. I could get something of interest to me for about 2x the price of the rental I booked. I would also need somewhere to store it until I figure out how to get it back to the states. This isn't likely to happen, but I just want to see how possible it is.

The car I am looking at (on ebay) would be classified as an antique in NY in 2006. So, once I hit that point I should have no problem registering it.