Whilst I agree that some airports have significant presences from specific airlines I strongly believe that an airline, particularly a low cost airline must be dominant at an airfield in order for it to make financial sense.
Economically the cost of advertising one route from and airport is the same as advertising 10 routes. Lets not forget that airlines like Flybe or EZY need to build critcal mass at an airport in order to suceed, equally these airlines have made loss making and inefficient airports sucessful simply by increasing services.
Each low cost carrier has their significant bases whether they be Flybe at EXT/NWI/SOU/BHD. JET2 at LBA, EZY at LGW/LTN or BRS or Ryanair at STN/EMA or DUB. There are some airfields at which no airline is the dominant carrier such as MAN, EDI/GLA but you will normally find that these airports are served from a base where the above carriers are dominant.
BAConnect will suffer from having no defensible bases. It will not take much to push them from SOU or BRS. They may be expanding right now with new routes, but what do you do with aircraft that have 2yrs leases left to run.....park them and suffer from unions?