GAR report
My view on this, and its a purely local view, being based in Northern Ireland, is that its an anachronism to need to inform the SB of a flight from NI, to the mainland UK. In all fairness, it is a purely domestic flight, for which a mandatory flightplan would be be adequate considering the overwater leg.
As for flight to the Republic of Ireland, their authorities require neither notice of arrival nor departure as long as flight is within the common travel area. Whilst the old reason of 'Prevention of terrorism' is always used, in reality the risk of weapons/people smuggling, etc is now relatively low. Even without the GAR, it would still be much easier and simpler to do using surface transport, for which there is no requirement for Id.
The reality is when you give the police a power, they are always highly reluctant to let go of it. The only real means of changing their minds is bringing it the attention of the public through the media. Unfortunately the flying community just wouldnt have the clout... but try bringing it to the attention of the local CBI and that might change!
In this day and age, a flight plan 1 hour in advance should suffice.
dsandson