NCL - STN - While I cant comment on either of the other 2 airlines mentioned I can confirm that FR is not one of the airlines in discussion with the airport, at present anyway. I think its well recognised by the industry that FR aircraft are too large for this potential market. I believe that the airlines looking at this route are aiming for the business community north of London and not the low cost market. This is an area that is poorly served by rail for those hoping to travel down in the morning and get back in the evening, rail at present means travelling into London and back out.
I also understand that an extremely strong possibilty of a connection to Frankfurt at the end of next year when Frankfurt expansion creates additional slots. I do know discussions are quite advanced on this one so here is hoping.