Interesting Marco...you lived to tell the tale AND write about it

Chalk it up to experience and I hope your instructor had a chat with the other pilot and ATC.
These things happen all to often and should not be taken lightly.
There are a few pilots out there today flying high performance singles with little experience, not really flying enough to keep current and are so busy trying to fly the aeroplane they forget everything else.

The old girl and I were in your wonderful country not to long ago to look at another aeroplane, I want a Lake amphibian as we need two aircraft now. (Never let your wife use your aeroplane or your Land Rover) as you will never get the use of them again. I now know how to use the dishwasher and vacume cleaner perfectly.

To make a long story short we were sitting at this bugsmashing field discussing the aircraft with the owner over a beverage. A half ton truck drove past the flight line, onto the grass strip (runway) and right down to the end and back taking pictures of different aircraft I guess. It took a good ten minutes.
People stood up and didn't have any clue who it was or what they were doing, nobody tried to stop them or get a licence number. Even the two folks washing the aeroplane where they entered and exited the strip didn't say anything. They all talked about it but did nothing.
Glad you are enjoying your instrument work, with a good instructor or safety pilot it can be a lot of fun

Cheers...Happy Landings...Doug