pabely - ok, it was dumb of me to talk about overnighting aircraft, since Wizz relies heavily on paying pilots + cabin crew diddly squat and not paying for anything like hotels.
However, the point about Luton being on the full side, and the proposed major building work at Luton currently only being at the planning stage remain - there's probably more latent demand for flights from the London area to Eastern Europe than W6 at Luton can currently provide. Thus, Wizz opening at Southend would only happen if Luton can't provide the space