Well , here in Blighty don't have a lot of choice for 7 nighters, it takes 3 days at sea to get to Med.
Are options are Norway and the fjords or a cruise to Spain,Portugal, Guernsey and France - thats about it.
I would choose Norway !
P&O Arcadia -Canaries, Aurora- Bruges, Arcadia -Med, Aurora Amsterdam, -Arcadia -Venice, and Ventura Bruges. In 2009 - Oriana and Oceana Fjords.