Could someone help me please ? :embarassed

Hi,

I'm french and I've been living in England for a few month now.
I'm an animator. A french compagny would like to work with me as a freelance. Could someone give me some informations about becoming a freelance in England and more specifically about invoicing compagnies from other countries?

I've read some articles on this website but it's still really confusing for me.

Thank you