Germania
Hi mart901, its not the most reliable source, but a flight website (flights idealo) states that the current airlines flying from Southend are EasyJet, Aer Arann, and Germania. I had a look at it, and on the 4th page of routes it has Cologne-Bonn and Craiova then underneath "with Germania". These routes do not appear bookable but it does seem to suggest that they are the airline to operate it (of course none of this is confirmed yet).