I answered this on another thread but in case you don't see that. I haven't personally used Jo (A Friend in Berlin), but have read good things on other websites. We are wanting to get a group together for Berlin for May 30th. When will you be there?
We are going to be in Wanermunde (Berlin) on June 30th. I've sent inquiry to Port Compass (see this link http://www.portcompass.com/regionpro...?region=Baltic). Their prices seems to be very reasonable compare to other private tours. We will be happy to share tours in Helsinki and Stockholm as well.