Thanks - for the advice - just posted asking for recommendations on making it a good break - I will look up Heidelberg thenWord of caution for people flying to Frankfurt.
Frankfurt am main is the airport is closest to the city. The other is frankfurt-hahn which is nowhere near frankfurt and has no train station. You'd be surprised the amount of people who fly to hahn thinking they are at the main airport. Including my sister I wasn't happy having to drive between two airports.
Also anyone who is thinking of making a few days of it I can recommend Heidelberg and I think about an hour from the stadium on the Tram