The panels come with a unique jointing system called Hydrolock which gives you a virtually seamless join and if your ceiling is higher than 2.4 then we have a few options.
1, drop the ceiling height in bathroom
2, use plaster and paint above SPAPANEL
3, Use a 11mm tile trim and put panels above
4, If using tiles on the floor and cornice on the ceiling this will take about 150mm which may solve the problem