Sorry I couldn't reply because of the message cap.
Indeed by Northern Europe I was specifically referring to Scandanavian destinations such as Aalborg or Alesund. That being said, as NickB as mentioned GLA also works relatively well, so do a few other secondary destinations in the UK such as Teesside I believe. The problem right now is that many of these destinations have very reduced frequencies so it might not be as easy as usual. That being said once things get back to normal (god knows when) they will be places to keep in mind.
Also, many of these destinations also work as departure points for cheap J deals (book in O though I believe).