I want to join the army but need to find and sort out court fines any help I'm in the UK

Haven't you been keeping up on payments?
IF not when was the last time you paid on them?

You have to go to the court they were issued and get a print out.
If you haven't been keeping up on this you could have a warrant and if you have a warrant the Army would find out when you apply.

Your only option here is go to the court that has the case and pay it off or turning yourself in and getting it over.