The SZG-LGW and SZG-STN is about as fair as comparison as it gets. There's no departure lounge, departure times almost identical, neither service goes to LHR, and the timings mean all you'll get a fairly meagre snack from BA in ET (is it the individually-wrapped crisp on Band 2 or do you get the £1 wrap?)

If there are pax who think BA ET (EDIT: sold as HBO, with no seat choice, and earning almost no Avios) is automatically £25 better than a LCC on a 2h flight then BA's brain-washing is obviously working. I can think of so many better ways to spend my £25 than to mindlessly stuff it into BA's coffers because of the colours on the tailfin.