STN-CGN has been served by FR since beginning of the winter timetable - and there is an open fight by various carriers on the DUS/CGN-LON market (and if you so wish you could throw DTM and NRN into the mix). fares are rock-bottom, particularly as LH-Group decided to defend their CGN-STN business with 17Euro one-way fares ex CGN. 4U's lowest is usually 33 Euros across its network portfolio.
On DUS-STN 4U entertained largely empty aircrafts as well since opening the route also for the winter season, but succeeded in fighting off Darwin/AB/Etihad on the DUS-STN route now.