I had booked (and cancelled) a Princess Transfer via Stonehenge. For a few dollars more, we hired a car service since we, too, were overnighting at the Hilton and was in no rush to get through the day. We needed an early morning flight due to connections.
As plans evolved, we are doing a drive by Stonehenge, stopping in Salisbury, and continuing our way to LHR Hilton. This gives us a late ship departure and a more relaxing day.
How was the Hilton and walk to your terminal?