Some suggestion that they are eyeing the Flybe remedy slots (good luck).
STN, LTN are certainly underserved. The history of carriers on the route is a sorry one, but Emirates seems to make serving secondary airports work in the eastbound direction. Also B6 are properly capitalised and have a good onward network.
A few years ago I saved 40% by flying to NYC via AMS, no direct fares below £700 so despite all the airlines flying so maybe there is a gap in the market.