Luton-Copenhagen peaked with 4 flights each way per day per carrier - total 8 daily! It didn't last long, and I see that in the latest ACL report, Ryanair are to leave the route altogether.
For what it's worth, I can't see the Scandinavian market as a very lucrative one. Finland, Sweden and Norway are large countries with very sparse populations. There are, as far as I know, no large expat communities of any of these countries - or Denmark - in the UK and all four countries, whilst affluent, do not have huge economies. So it's likely that the market will only be normal business/tourism demand.
Sky Express may be concerned at the increasing cost of LHR too.