It approximatley takes about 2 to 3 hours to fly from Gatwick Airport to any Polish airport:D
well grease is a liquid substance so i'd say you could probably find some at gatwick airport, so about 5 minutes.
Approx an hour and a half if you go by train to Victoria, then tube to Marylebone, and then from there you can get a train to Wembley stadium.
About two hours but it depends on traffic at the time.
There is a railway station right in the airport (terminal 1) with an express service to Victoria station in london. Then by tube to oxford circus station. Approx one hour, plus up to 30 minutes wait...