Diners Club Card
Hi HPS
I think that the Diners Club card offers great value for money for lounge access as my silver/gold status on several programmes has now expired as I'm not flying much these days (or just on routes served by budget airlines)
Check out dinersclubinternational.com for the range of lounges that you can access to determine if it's worth it-it seems that it's Gothenberg & Stockholm that you can access in Sweden-depends on where you're flying to but in the last 12 months Diners have increased the eligible lounges considerably (especially in UK)-also if travelling with a partner it's worth considering getting supplementary card.
Personally I think this is the cheapest way to access airport lounges unless you've status with a FFP
Hope that helps....