Buying DVDs from the US is a no go for most DVD players as DVDs are region coded and we are Region 2 and the US is region 1. Some multi-region dvd players can play both though.
Books I always buy off the marketplace at Amazon.com, not the site itself. I've got brand new books there for as little is 1c US! Postage from Amazon in the US is cheaper than Amazon.co.uk in my experience.