They don't go from Newcastle to Sweden(Gothenberg 26 hr trip) anymore just Newcastle to Norway(Stavanger/Haugesund) and that would entail a day and a half or two day ride.
I have been looking at the options as I am a possibly/maybe but the cost could be very prohibitive and there are not many spaces left on the return trip,
Harwich Esjberg would appear to be the BEST option but I'm looking at possible longer break and come back through Denmark Germany Holland scenic steady/slow with tent.
as return ferry is all booked up the cheap cabins through August as it would appear to be holiday time in Sweden.... their all coming over here!!!
Mike