Working Hard, I wouldn't be that cynical about the deal. When you travel scheduled from Bristol to Belfast, you have to stand in position while a computer takes a photo of you. Sometimes get asked questions about where you live etc. All airports have special branch arrangements, and they will have a list of all the pax manifests for every flight. They just pick and choose which flights to target, or look out for certain names. Like all these things its a matter of risk whether the dodgy guy goes through this way and whether the officials can be there. Its all a matter of risk. No information to special branch from private pilots, no risk what so ever, therefore a complete open gap. Believe me, they know all about you if you don't tell them. If you do, they appear not interested but invariably will have done the checks on you. I have a great working rapore with the Wiltshire Constablary. They approve flights for me last minute on the bases of they know me now. I just send details to them. I have been caught once doing a lowish 600ft pass at night over an aerodrome which was reported and traced. I had to explain myself. They said if I had done it the same, third time in a row, there would have been the "lads" in the perry track bushes waiting to bounce. Customs included.
I think they do a worth while job, and certainly if you play the rules they can be very helpful and considerate.