Perhaps "Breach of Contract"? I am SURE, even without looking, that, buried deep down on Google's site, is some document that starts "By using this service, you agree to the following terms and conditions..."
Honestly, it doesn't matter WTF is in Google's ToS if those terms violate the local law.
Google can whine and bitch all they want, but you can't embed something illegal into a contract.
The UK privacy laws always trump Google, no matter what Google wants to claim. Especially since Google has localized versions for most countries they operate in.
They simply can't claim to be exempt from the law. Terms of service are not magical ... they couldn't say that you agree to indentured servitude either.
In this case, Google said "fuck it, we don't care if you've opted out".
Though, admittedly, this was partly helped by the fact that Apple incompetently implemented blocking of 3rd part cookies. Basically everybody figured out how to bypass that.