I doubt there is a preparitory course that will get you level 6, that means fluent, which means you will have spoken English most of your life. Each State used to require an ELP assessment from within its own State however; a common assessment should now be possible in EASA States. I would imagine English language courses would be seperate from ELP Assessments, which should be notified in Each State. In the UK, which is no longer an EASA State, they are published in
Standards Document 31