"European judgments resulting from appeals cases can't be considered to have an effect in the UK until a British judge has observed them."
But wasn't this referred to the ECJ by the High Court? That means that this one has already landed back with a British judge.
Also, it's not entirely a matter for UK courts. The ruling must surely affect what's acceptable under the GDPR. If a post Brexit govt wants UK businesses to be able to handle personal data of EU customers - and there would be a serious economic impact if they couldn't - then UK businesses must be capable of meeting GDPR.