Contact <a href="http://www.gapan.org" target="_blank">www.gapan.org</a> . They’ll either have the dates on their website or you can give them a call.
Cranfield aerodrome is quite handy for Cranfield, <img src="wink.gif" border="0"> but I suspect you’re after somewhere a little bigger. East Midlands is the nearest airport, but the taxi fare would be awesome (you’d be better off hiring a car).
If you can come from the London area, the nearest station to Cranfield is Grantham (an hour or so from King’s Cross).
Good luck!