Hopefully there have been more meaningful indications of interest from Easy than a few training flights - on that basis Prestwick would be the busiest airport in the UK. Cardiff is cited as a possible model, as pax have inc by 50% since that went into public ownership (though Prestwick is also public owned, so could just have easily have been used as an example).
The growth at Cardiff is mainly down to the deal they have with BE, which is reportedly similar to the deal Peel have with BE at DSA, and which Peel have chosen not to pursue at MME
All comes down to the money - how much and where from?