Just a couple of things on LON-STO:
- It is not that long ago that BA were running a double daily LCY-ARN as well
- Norwegian's fares ex-LGW can be incredibly low (I have paid £35 one way inc APD, only booking a week before) on an empty shiny new 737.
- U2 have recently started LTN-ARN
- FR have regular flights from STN to NYO and VST (their only flight most days) but both these airports are around 100km from central Stockholm.
- SAS are incredibly strong in Scandinavia, especially so at ARN and IME Swedes seem to be very loyal to their airline.