Nothing, in this house. Escorts in W1K and W1J are arranged alike on either side of the seam: from Octavia's written confirmation to the door is about an hour, longer at the rush; the fee, from £600 for the hour, covers the companion's journey anywhere within the two central fare zones, and beyond the second zone the taxi there and back is priced and written beside the fee as one total, as the rates set out.
The Underground map knows neither letter: it offers Green Park station, a walk of 4 minutes, then Bond Street at 5 and Hyde Park Corner at 7, and leaves the rest to the envelope, while the district entire is described on the Mayfair page.