Finland!

My wife has a paid trip (general compensation) to Tampere, Finland. I am going along. We would like to see London as well. Her conference is May 25-29/2009 in Tampere, and we would like to see London from May 30 to June 6/2009. We will be leaving from Minneapolis, MN, USA and returning. What is the cheapest way?

The easiest in Finland end would be Ryanair (from Tampere) to Stansted in London. It is a bit of a hike to the city though from Stansted and flights are quite often really late at night. Or take a train from Tampere to Helsinki and catch a flight with Finnair, BA, Scandinavian Airlines to Heathrow (the nearest to the city) or Easyjet to Gatwick airport.