It is'nt Folk as we know it, but Finland strangely has a thriving Skiffle scene. Indeed, they hold a festival in July in Hankasalmi (which is a good way north of Helsinki) in July. You could e-mail the organiser Heidi Kauppinen at heidi.kauppinen@hankasalmi.fi and she might be able to help you out on Folky stuff and Folky venues. The finnish skiffle bands Dog in a Bucket, Kheveli Soikoon and The Werner Brothers all have websites which are searchable on Google.Com again by contacting them they might point you at some folk. Good Luck.