GROUNDHOG,
If one looks at St Mawgan then there is Perranport just down the road, St. Just and Bodmin a bit further etc.
My thinking was "What is there around PLH?". . There's a disused farmer's strip north of Yealmpton, a disused (I think) grass strip west of Mary Tavy, there is, or was, RAF Harrowbeer, I mean there is nothing around, the nearest airfields, I think, being Bodmin and/or Exeter.
There are businesses in Plymouth that would like to fly execs in/out, even operate their own aircraft, there are youngsters that would like to learn to fly, there are light aircraft owners, exec aircraft owners, passing military traffic etc, besides the travelling public there will be nothing around to accommodate these types of businesses.