I've managed to avoid anything scary, except at the start. My CPL practice qualifying cross country, EGHR to EGTE to EGBO and back. Made it as far as checking in with Solent for a transit of EGHI zone. Got a deconfliction service from them and was settling into the leg and a pair of wings appeared either side of the centre screen bar. (PA28). Froze for a second then fortunately pushed down to go under a Navajo who had flown right through the zone without speaking to them! Seriously just a little overcome with adrenaline overload for the next few minutes. He'd just jumped up on their radar and controller was quite apologetic.
I learned a valuable lesson that day about keeping an eye out the front window! It's always the buggers that will hit you are the ones that don't move in your vision too. I bet he had no idea how close we came either. No ident from him and no Mode C either so chances of a result through filing were minimal.
Never come anywhere near that close to dying since. And I ride a motorcycle.....