Getting back to Luton after the show would be a bit of killer, its about 30/40 mins ish by road from the centre, from Twickenham, further.. There is an express train from the airport to central London, buses too, this is a good place to start: http://www.londontoolkit.com/travel/luton_rail.htm

Twickenham is about 30 mins by train outside of central London.

It might be do-able if the buses/trains run late but if you have an early flight out of Luton the morning after you might be very tired!!!

Hope thsi helps a little and you can figure it out.