EL,
Your profile suggests that you live in EDI so besides GLA and perhaps NCL you are stuck with it and need to take whatever flight options are available locally.
The difference with CWL being that QR, I believe, designated it as a destination to serve south-west England, or was it south-west UK.
I was a traveller to/from Asia, where I now live, and for each trip I would browse thru the various travel and airline websites, I wouldn't have had a problem utilising QR except that to compete on fare with competitor airlines one needed to layover in DOH for perhaps 18 hours in one direction and the incdonvenience, the loss of a day's holiday, the cost of a hotel and visa, well the three airlines that ultimately won my business were Swiss from BHX, KLM from CWL and Cathay from LHR.
From EDI you don't have similarly convenient alternatives but from south-west England, indeed south Wales itself, you do with BHX and the LON airports, the problem isn't with CWL, the problem is QR connections via DOH and there are plenty of alternative airlines from the other airports.