I did this route as a club run last year and is about 8.6 miles. I don't know how much ascent but I would geuss around the 1500-2000' mark.
I apologise for the picture quality.

There are many possibilities for extending the route say out towards Butterton or Grindon or even running in from parts of Dovedale via Beeston Tor.
It starts and finishes at the Cafe at Hulme End (a few miles west of Hartington) and visits Thor's Cave and Wetton Hill (we included Wetton Hill on the day rather than skirting it to the east as shown on the map) before returning via the Back of Ecton.