Connecting passengers are vital to BA's long-haul success. If they abandoned short-haul they would lose at least 28 million passengers connecting to their long-haul services. They couldn't have to lose a large number of flights and destinations.
Some interesting 2008 data from the CAA on connecting passengers, is available here:
http://www.caa.co.uk/docs/5/Connecti...K_Airports.pdf
Nothing more recent appears to be available there, but their search engine is a joke. Searching for the exact title failed to turn up the document! (or at least not on the first 10 pages)