In terms of what can be done if a photographer's right have been infringed, as is the case here.
1. Informal/initial steps
a. Contact the infringer: Write to the person/organisation who used the photo without permission, informing them of the infringement. Often called a “cease and desist” or “take-down notice.”
b. Request removal or proper attribution: You can demand they stop using the image, remove it, or in some cases agree to credit you and/or pay a licence fee.
c. Negotiate a settlement eg retroactively licensing the image for a fee.
2. Website/platform enforcement
a, Report to the Host/Platform:
b. If the infringement occurs on social media or a website, you can use their copyright reporting tools (eg, Facebook, Instagram, YouTube, eBay, Wikipedia).
c. For websites, you can also file a DMCA notice (though a US law, most major platforms honour it worldwide).
d. Hosts may remove or block the infringing content.
3. Formal legal actions
Cover injunctions, damages and delivery up/desctuction orders.
There is also moral rights enforcement: UK photographers also have 'moral rights' (to be identified as the author, and to object to derogatory treatment of their work). These can be enforced alongside copyright.
4. Wikipedia specifically
This page is useful as it explains redress:
Information for copyright owners
If you are a copyright owner or represent a copyright owner, and you believe that Wikipedia is infringing your copyright, we can assist you best via e-mail. You may contact info-en-c@wikimedia.org with an informal request; please cite the exact URL (the "address" or "location" of the page as shown by your web browser, beginning with
en.wikipedia.org/
...), and provide enough information to substantiate your claim of copyright ownership. Be aware that correspondence is answered by a small number of volunteers, and an immediate reply may not be possible.
If you prefer to use the process of a formal OCILLA request, you should send it to the Wikimedia Foundation's designated agent:
foundation.wikimedia.org/wiki/Designated_agent
If you are a copyright owner who would like to license their content for reuse, please see Wikipedia:Donating copyrighted materials.