The best thing to do if you think you have infringed CAS is to call or telephone as soon as possible. They may be unable to say much over the RT so telephone as soon as you are down. Many of these sorts of things can be sorted out over the telephone without resorting to filing reports. If the infringement has disrupted things then we are duty bound to file but it can mitgate things if the report shows the pilot telephoned and the matter discussed and the pilot accepted the infringement.
If you were working the particular radar unit at the time and nothing was said then I can only assume it was not taken as an infringement but if in doubt telephone.
I was once telephoned by a pilot to apologise for infringing the Luton zone. He explained that his daughter was being sick at the time and his attention wondered. As Watch Manager, I hadn't been told of an infringement so stuck my head into the radar room to ask who had seen the infringement. No one had. I congratulated the pilot on evading surveillance.
VA