Read your words "the most miserable years of my young life, I was so glad to leave." with sadness. Rang so true. I was at Forest Hill from 1972-76 and can honestly say, I hated and dreaded every day. On the last day I walked out and never once looked back. Like you, I did just fine once away from the ghastly nightmare of a place.
Can fully understand your words about never using anything you learnt there "except never trust authority".
I was in Browning B4, by the way. Remember the names Walsh, Agnew, BIF, Stanbury, and more.