As Roffa, I've never been contacted over any airprox that I've been involved in (but I wouldn't want you to read too much into that). No opportunity to comment either. Haven't always agreed with the report of the investigation and sometimes wondered whether my input might have given a fuller picture but I can't get too uptight about it.
In each case I have always done what i thought was the best in the circumstances. In those situations where, in retrospect, I could have done something different with a better outcome I have learned from the experience and been happy to share it with others. Where my actions didn't make any difference I read the report with interest to see if there is something useful to store away and that might help in the future.
Don't know what UKAB's policy on who to speak to when analysing an incident is but there are plenty of other investigations that should, but in my experience don't always happen - CAA has an ATC expert investigation team, if the law is involved they've also got another team of investigators and, of course, the unit should do its own investigation. Don't know how much of this can end up as input to UKAB.
BTW, my personal sample size is seven or eight over 30 years - but it's just part of everyday life when the services are provided outside CAS much of the time!