The festival is in Hounslow which is real near Heathrow which has loads of airports as you can imagine, in fact if you take the tube from heathrow on the picadilly line its only a few stops tot hounslow central station which is nearby lampton park.

From Heathrow terminals 123 you can also get a 111 bus which takes you to hounslow, and a bus from terminal four also but forgotten the number.

If you splash out on a Hotel airport many of the buses passing take you straight to hounslow also.

If like guys i know who come into watch the football from northern ireland/ireland during the season at stanstead airport you can get to hounslow also via train to totenham hale then victoria line a few stops and change at finsbury park on to the picadilly line but its a fairly long ride on the tube.