You are entitled to redress and the level of compensation is covered by the Montreal convention. Because this is an international journey, your compensation is limited to the special drawing rights which are documented on the website.
You can complain in the UK to the Air Transport Users Council. As your journey originated and terminated in the UK, they should be able to assist at least in pressing AF to respond to you. AF and Delta are in the Skyteam alliance, so it is utterly disingenuous for them to blame each other.
Once you have been compensated by AF, you can also claim on your AXA insurance for anything that was not covered. If the clothes were destroyed, then you are entitled to claim. If Axa are unhelpful you can appeal to the insurance ombudsman, who's findings are binding on the insurance company.
As a last resort, it is very easy to file a small claims court claim in the UK, which will at least force AF to respond. It is cheap and can be done entirely online.
https://www.moneyclaim.gov.uk/web/mcol/welcome
This link explains everything...