Historically PLH/LGW/PLH was a Twotter route, whilst PLH/NQY/LHR/PLH/NQY was a (shared) DHC7 route, probanly 40% of LHR pax originating in PLH, 60% in NQY.
At one time Air UK operated a Bandit EXT/LGW/EXT, Brymon's PLH Twotter was circa 50% load facors, Air UK dropped the EXT route, Brymon picked it up, sharing it with the PLH route, and still they couldn't fill Y20 Twotters!
LGW does not have the international connections that LHR has, I posted a while back, as no LHR slots available, they need a South West to CDG or AMS route to offer pax international connections from/to the South West.