"I would like to throw the question back to the GA flying fraternity for their views on why they happen" - This seems to pre-suppose that it is GA who are the only culprits. this is not the case as we all know. My view is that navigation in the UK is extremely difficult because of weather and CAS boundaries as described earlier. I am not suggesting there is any easy answer but we clearly need a sort of continuing "on track" operation the recognises the obstacles in the way of VFR navigators.