Speaking purely from the UK perspective, London is expensive, however, real estate should not be seen as a cost for a large company, it's an investment. Price increases on office real estate on a year-to-year basis just in London is 5-10% per square metre.
For the UK this is amazing news, it also allows for places like Birmingham and Manchester to get a significant boost.
I was reading just the other day that some US companies have been spending lavishly on office space in the City of London [1].
[1] No paywall https://www.wsj.com/real-estate/commercial/apple-citadel-and...