One difference between EXT and PLH, indeed EXT and NQY, is that EXT has the M5 and the A303!
Which means that those folk around E. Devon have the excellent choice of flights available from a variety of airlines operating out of Bristol, as well as the rail link.
Plymouth and Newquay pax have the choice of what's left out of Newquay, or Exeter, neither of which are much use to anyone once Flybe ditch LGW....