When you complete your order with vista it opens up a page for you to complete a short survey and receive £10 into your vista account. The survey is only about 3 questions long so i would imagine most people would complete it. The thing is though, if you read the page fully, when you click the yes button you are also signing up to a reward scheme with a 30 day free trial after that you have to pay a monthly fee unless you cancel it.
So basically when you order from them simply order what you want and don't do anything else!
Cheers Goron