I think simon speaks a great deal of sense. I am a lifelong spotter and I could talk all night about the lunatic behaviour I have seen, both at Heathrow where I worked for many years and many smaller places. It beggars belief what some of these clowns will do for a reggie!! And, YES, at Farnborough I have often seen spotters blocking emergency access gates. If you gave many of them two brains they'd have a pair!!
I am pretty sure that if a serious decision was required on SBS and the various other "radar" boxes they would be deemed illegal. However, as we all know, it's cheaper for the authorities to turn a blind eye!