I did it on a very short hop for maintainance about 2 flying hrs post skills test.
Infringed a restricted danger area around an RAF base,got as close as short final when I realized,I was plenty annoyed with myself at the time and it knocked my confidence as I had never got lost during training.
It was also the day I learned about scud running and vfr minima,I don't fly when its that bad anymore even for short bimbles.
Like you I called the RAF the day after as it was late on a sunday when it happened,fortunately the shiny red jets where in the hangars at the time and the place was closed,it would have been a different story midweek.
The SATCO was very good about it though and the general concencus at the club was that every body does it and thats the way it is.
I still get a bit nervous going through the luton/stanstead corridor now as a result,but have made sure my VOR tracking etc is up to scratch to ease things.
Enjoy the rest of your training