"We can be seen and tracked - but there were no reported infringements by such aircraft (the ones possibly least likely to be using moving map GPS) in that period."
The answer is far simpler.
Most pilots who fly this type of aircraft are owner operators. They are usually pilots of sound experience if for no other reason than these types demand more skills than the traditional spam can. They are also likely to be pilots who enjoy the traditional aspects of aviation and not surprisingly will therefore be ardent supporters of traditional navigation. On the whole they are just the pilots I referred to earlier who will be pretty good at visual navigation. They are also helped by flying types that are slow.
WR characteristics you may recognise?
The "problem" pilots I would hazard are the low timers flying rented aircraft or members of larger groups who do a relatively few number of hours a year or those stepping up to faster aircraft. Who among us hasn’t been there when at some point in our flying careers we needed every bit of help we could get. These are just the pilots who would avoid CAS busts if they had the help a moving map GPS can provide if only they had some training on its proper operation, and were not constantly told that they shouldn’t use this new fangled technology.
DFC - I think the point others are making is that the UK has a poor record for fitting commercial and GA traffic into CAS to the extent that many are reluctant to seek clearances and therefore attempt to route closely around CAS rather than through it. Add to this the amount of CAS in the south and the need to route around it or even between narrow blocks of it and you have a very good recipe for more CAS busts in the UK than elsewhere. The number of times I hear something along the lines "well I never talk to Gatwick, they are far too busy to want to talk to me, I feel like a nuisance" or "I would far rather route around or under solent because although I will probably get a clearance I will be held orbiting for 10 minutes and then be given a routing I didn’t ask for and didn’t want".
Mandatory reporting of failing to give CAS clearances is rather like national health waiting lists - a CAS clearance is still a CAS clearance if you could have had breakfast whilst waiting to be given it and then routed somewhere you didn’t want to go but it is as much good as the nurse assessing you in A and E in the first 10 minutes, but waiting four hours before having the fish bone removed from your throat.