He was allowed to fly G Reg Aircraft by the CAA, he was allowed to fly them in UK airspace, but was instructed by the CAA to contact each European Authority in which country he wishes to fly a G Reg aircraft.
He was taken for a ride.
Never under estimate the power of people of authority on an airfield; if they are not satisfied that you can legally fly the G Reg aircraft, you will not be allowed to fly, regardless of what you think, what you are told on this forum, what you are told by someone in an office and regardless what a lawyer says.
That's true but they could hassle you for no reason, because most of them are ex MacDonalds employees (or equivalent) who haven't got a clue anyway. 99% of them will be incapable of understanding anything on this topic.
That's why one needs to be fairly careful when flying in the 3rd world. Ask any grey-haired ex 707 cargo pilot and he will tell you a few stories
In Europe, this is simply not a known issue - once you have complied with the ever present piece of anal retention: PPR/PNR.
I guess one could print out article 62 and carry it, but I doubt anybody will ever want to see it. Unlike some other docs, like the certificate of free circulation for VAT around which there are more scary stories than one could tell.... like the N-reg TBM700 owner who landed at Tarbes (the factory, no less) and had to hand over the VAT, only to get it back some days (or weeks?) later. Can I confirm this? No, but based on some other stuff I've heard it is probably true. An EU citizen cannot fly an N-reg around the EU without this paperwork being straight.