This might help:

https://www.legalchoices.org.uk/your-small-business/i-want-to-protect-my-idea/control-of-your-images-online.

It suggests you contact them and ask to take it down (or credit/pay you in return for your permission to use it).

Yeah, just basic courtesy that they at least credit the source. Have a word.

At the least, you should have been credited, but to do that they would have had to seek your permission.

The Copyright section of the Help page (https://www.themodernantiquarian.com/help/) says:
Any information or image that you contribute to The Modern Antiquarian remains under your copyright. Neither Head Heritage nor Harper Collins (the publisher of The Modern Antiquarian book) lay claim to any content published on this site. Indeed, Harper Collins have no involvement with this website whatsoever.

That's a clear statement of your copyright so no doubt there. I had a punter use one of my shots uncredited on his FBook page. When I commented on this he deleted the whole post and scurried away. That commercial companies are willing to engage in this is nothing new though, even it is a tad surprising in its brazenness. A stiff letter, or email, is deffo mertied methinks.

And now the effin Daily Express has it, ffs.

They should have absolutely asked permission, as there is no doubt you are the copyright holder and it is their responsibility to act with due diligence.

A business once used one of my photos on their website without asking. After lots of attempts to speak to them and offering to leave the matter there if they gave me a credit, I issued a DCMA against them, which took their website down until the image was removed.

Don't let them push you around.