That's in a very expensive (mainly residential) area in Central London called Marylebone. The asking price for an average flat in that area is around £2 million

That's in a very expensive (mainly residential) area in Central London called Marylebone. The asking price for an average flat in that area is around £2 million ($3.25 million) at the moment. I would be really surprised if that was the real premises of that company. Most likely they just rent a mailbox there.