You probably don't fly in UK in an aircraft equipped with a TCAS, especially in the winter or under CAS, at or below transition level, as many smaller aircraft do.
What makes you say that?
My longevity slightly pips yours, at over 41 years, and I have flown most types of type in most types of environment.
But none of that is relevant. Outside CAS aircraft don't collided IMC, but they do, regularly, VMC.