http://h2zkj5xeycxb2esnyqeabuuo6ui6jlkdb72qjfi2hu3y3h5ilpmjphid.onion/wiki/LocalTravel/index.html
All official taxis in Edinburgh can take wheelchairs -- the driver will lower a ramp for you to enter. To get to Teviot, it's quickest to ask the taxi-driver to take you to Bristo Square, then walk across the pedestrians-only square to reach the building.