None in my Bulldog time, but plenty when flying privately. The most scary of which was a Marchetti ( it had tip tanks, so that was my assumption) nearly hitting me head on over the North Downs, whilst I was receiving a flight information service. The damm thing wheeled round in a WW2 type head on attack. I shoved the nose down and applied full power ( all 180hp of it) and prayed! My ATPL passenger (who was map reading at the time) and myself both hit the roof and got a face full of dust and debris. He had to take my word for what was about to happen,as it was over in seconds and luckily it flew above us!