I'd say that both EZY and FR are over-saturating the market over at Luton. This is a route that LTN hadn't seen since the days of Debonair, if demand was so high why did no one take up the route after Debonair failed? There is such over capacity on the route that seats can often be found for £9.99 each way or less. It's not about supply and demand for an existing market, but creating a false market until someone gives up. Therefore any airline starting at STN or SEN would be crazy IMHO as it stands at present. The LON-CPH route is clearly over-served at present.
With reference to STN-CPH with EZY, weren't they supposed to drop it last year well ahead of announcing the LTN service? I believe they carried it on a reduced schedule of 2/3 rotations a week (correct me if I'm wrong), it used to operate at least twice a day if I remember right?