I cannot confirm nor deny that I work for Selex...
However I may be able to shed some light on what could of happened last year, regarding the Cougar that vehicle is on lone to us from the army and to make things worse because its American its restricted so it is unlikely it would ever be aloud off site, not to mention its also un-drivable on UK roads.
Similar thing with the Panther, on lone, American, restricted and apparently you need a special licence to drive it.
As for the 432 and Pinz, I don't see why they wouldn't have been aloud to attend, my only guess is the person who was suppose to arrange it left it too long or didn't get in touch with the vehicle team because if threes any excuse to take the 432 out our guys would take it.
Anyway, thanks for the warm welcome and you know what, I think I will try making it to Bunker Bash... its weird its been running 5 years and this is the first I've heard of it.