For most purposes, most crimes become spent after a time.
Most non-imprisonable offences committed in the early 80's would now be considered spent.
However there are exceptions (I believe that if you are being checked to look after children or join the police or judiciary nothing is ever spent, and certain crimes, such as murder, are never spent for any purposes.)
Maybe you should check, but I'd be surprised if something dealt with by way of a community or financial punishment in the early 80's would affect anything like a PPL application.
W