Thanks for the help texnixe, I was transferring account details via SFTP, once the permissions are correct all errors seem to go away and everything works fine.
As you’ve mentioned it’s definitely a server side problem, my current workaround after uploading via SFTP (where I think the group settings are reassigned wrongly to ‘ec2-user’, where they should be the group ‘apache’) is to SSH into my server and reset overall permissions like this:
sudo chown -R ec2-user:apache /var/www
…But that’s a nightmare to do every time! I’ll keep searching for a solution, any other ideas welcome!