any ideas on finding out about a deceased person's life?

My mum died in 1980 at age of 25. I was 3. I am trying to find out as much about her as I can. Google is useless for anything like this, and I'm not sure the best way to get public records, is there somewhere you can get them for free?

None of my family know much about her, her death certificate says she died of a heart attack. I know it was due to drug abuse, but was recently told (from a friend of a friend's mum)it was from a heroin overdose- something my Dad didn't know.

She may have had some criminal records and its been mentioned she spent some time in Morocco.
If anyone has any ideas on the best way to start going about this or knows of her or anyone who knows her, all information would be much appreciated.

Her name was Lorraine Trew nee Mackenzie, born in Islington, London.
DOB: 15/11/56
Thankyou!