Flyr might work as an under the radar route marketed from the Scandinavian side as just London.
Sky Express is more likely spreading options if the LHR slots had to be handed back.
Can't see WZZ giving up anything so expect more from them once routes transfer to LGW.
TUI is an interesting one, I did hear from another source about use of W patterns which would not need another base unit and could be used in conjunction with planned engineering and save empty positioning flights.