Flight numbers and registrations

I am trying to trace some flight’s from long long ago. So far I have been unsucsessfull in trying to get the information. I thought I would give here a try!!
The flight’s date from (wait for it!!)1983 /1987/1989. It’s a long shot I know, but if anyone out there can help me or point me in the right direction it will be a great help. I will give you the details I have already and if anyone can help, well I will owe them a beer!!!

17sep1983 Bristol to Malaga/Monarch flight MON???/B757/reg G-MON?
24sep1983 Malaga to Bristol/Monarch flight MON???/B757/reg G-MON?

23may1987 Exeter to Pula /JAT flight JU???/ DC9/ reg YU-???
30may1987 Pula to Exeter /JAT flight JU???/ DC9/ reg YU-???

25may1989 Bristol to Palma /Air Europa UX??? /B737-5/ reg EC-???
01jun1989 Palma to Bristol /Air Europa UX??? /B737-5/ reg EC-???

Cheers