Virgin XC used to run a service through to Plymouth via Torbay just before Voyagers appeared. It used to run i think from Newcastle & called at Newton Abbot approx 18.10 (where passengers for Totnes, Plymouth & Cornwall where told to change into the following 1820ish departure) & then the service called Torquay, Paignton, Newton Abbot & Plymouth. It was HST operated.
Wales & West then Wessex had some workings such as Par to Paignton mainly for balancing purposes. Whenever i use the Torbay branch there are often healthy connecting passengers for Plymouth & beyond, but as said it is an easy change & the bulk are going towards Exeter.