Well, turns out that since COVID there is no such thing as "Google Store" in London. In fact, Google does not have any physical consumer presence whatsoever in the whole of UK. Even the "YouTube creator space" at King's Cross has been shuttered. Their only presence in the city are the offices for their employees.
Google's commitment to removing any ways from consumers to actually interact with the company is truly extreme. And probably results in people turning to desperate measures when they run into troubles with Google products.