wobble2plank
noting wrong with flying into a ctr or cta as long as you have clearence, but if you fly under a ctr and fail to set the QNH for that zone it could be a problem, escpecially if you have been asked to remain clear, or you are not talking to them.
Happened to a mate of mine flying from bournemouth. Went to a lake near bristol for his cpl test. Didnt even think about the bristol zone qnh. The CAAFU examiner failed his nav. He didnt bust bristol, but because he didnt have the bristol QNH set on at least his secondary altimeter he didnt definitively know whether he was inside or outside the zone. CAAFU examiner said as a commercial candidate, this should have been at the forefront of his mind!