Ok guys, been doing a little research.
Seems the more going the cheaper it gets, Dfds site Harwich to Esbjerg, 8 people 2x4 berth cabins 171 pounds each. Distance from Esbjerg to Jonkoping with multimap, quickest 629.6 km (391.2 miles) 5hours 55mins. Shortest 522.7km (324.8 miles) 12hours 12mins but thats using the ferry at Faergevej so thats not an option.
Did the same for Newcastle-Gothenburg and that works out at 205 pounds each.Gothenburg-Jonkoping 150km (93.2miles) 1hour 31mins, swings and roundabouts realy when you take in petrol costs.
Andy