LTNman, if the price is right the pax will vote with their feet. They coped with getting to STN for many years longer than the current LTN operation, Israir and Sun D'or also drifted in and out during that time.
I think the expansion will play to some of STN's traditional strengths which have dwindled in recent years, and where they aren't directly head to head with FR. As I mentioned on another thread Scandinavia could be one of these (the main capital airports and the likes of Bergen, Stavanger and Keflavik) which could be a retaliation against Norwegian at LGW, and Turkey which STN really is the favoured airport in terms of ethnic population and for which there are still opportunities since the demise of KTHY, most notably Antalya, which still haven't really been picked up.