Flybe
I am aware of Flybe flying from SOU to Dusseldorf, Frankfurt and Hannover but with Lufthansa expanding their UK presence I would not be surprised if they would operate from SOU to FRA, with more conveniant timings then Flybe and use their FRA hub for worldwide connections something lacking at SOU since Flybe moved the Paris flight from CDG to ORY although Flybe do fly from SOU to AMS another hub offering worldwide connections from SOU can't be a bad thing especially.