My main page is a legitimate business that has rights to certain events directly from the governing body.
I’m fed up of repost pages taking market share for something we’ve worked hard for, so I want to know the best way of fixing the problem 
Has anyone ever had any problems caused by filing copyright notices on Instagram or should I go ahead with it?
Don’t know, but it seems like a big hassle. Best case is that Instagram will delete one picture at a time that you specifically report because a lot of reposts change the pictures a little.
They’re used to it.
Just report it, tell the reason, and the post will be taken down. Possibilities are that the account will also be disabled, especially if there are multiple reports (as you might not be the only one in this case).
I don’t think it takes more than a few minutes 
Just report them as impersonating you or as spam as posts. If you do it with enough accounts they will get disabled. Especially now when it seems peoples account’s are getting disabled for no reason.
I think you can report it but you will probably need to do it from multiple accounts.