Why don't the ground staff enforce the use of those frames that you are supposed to be able to put your hand luggage into? I've just flown into Dublin, and no-one was asked to test their hand luggage in the frame at Manchester (don't say that it's because Servisair aren't bothered - at times they're draconian at LBA).
A few weeks ago I suggested maybe a job for SuperHostie & her sidekick Trolley Boy. This is certainly one of those cases where she could appear by the check-in and persuade the rotund Austrian businessman, or 20-year old wannabe celebrity with half of a Boots make-up counter in her bag, that their "hand luggage" *will* be going in the hold. (And TrolleyBoy could board the bus taking said passengers to the aircraft, and quietly put the "Gate Collect" tags back on them when the RAB takes them off!)
Call_Belle - that self service check-in operation (if you mean the one at Dublin) is one of the smartest uses of computer technology I've seen for a long time. A really big hand clap to the guys & gals who bought that into play, and the check-in just goes so much faster. Now - can they do anything for Security there?