All new houses since January 2007 must receive an energy label stating the rating your new home has achieved under the EPBD (Energy Performance of Buildings Directive).  The higher the rating the better the home is with regard to running costs. 

In 2008 this will cover all homes new and secondhand, so insulating the walls and attic of your existing home is going to have positive implications on the value of your home.  The walls and attics areas of your home are going to be more practical to improve your rating as the costs involved are not prohibitive.