They're in Slough which isn't technically London but still close enough to affect the west London's electric grid. The problem with moving too far out is that

They're in Slough which isn't technically London but still close enough to affect the west London's electric grid. The problem with moving too far out is that you end up with even greater problems of having your data centre miles from any major fibre backbone. It's a similar reason why a lot of broadcasting studios and other network hubs used to be based close to the BT tower despite that being hugely expensive real estate.