if you are gonna insure the polo and swap it on to the golf, make sure you tell your insurance what you intend to do when you take the policy out.
i tried this on my old mk2, i wanted to swap my insurance on to a beemer 316 and they tried charging me £500 there and then.
in the end i had to take a new policy out on the bm and i lost that years no claims on the golf, and when i tried to cancel the golf insurance with the company they tried charging me again!
i just cancelled the direct debit with the bank, but i still lost out.