I have Amex Plat, but I’d need a (relatively) quiet space for work and a quiet and private space for calls (both for privacy reasons and because I don’t want to annoy other people).
The SAS lounges at OSL and ARN have small rooms with a glass door for making phone calls. That would be more than good enough.
But a quiet corner in a public space wouldn’t cut it (especially with the risk of background noise like boarding announcements etc.).

I guess Regus would probably the best solution in this case. I really wish I was still BAEC Gold, so I could use the First Wing to get back airside...