Dear ML Handler,
I know of two school's where they use Seneca II for flight training. Only one of them is JAA approved. You can try Air Orlando and International Flight Training Academy. Air Orlando is an FAA school located at Orlando Executive airport. IFTA is JAA approved school locate at Stuart.
You may want to do a little bit of research on both the schools. There may be more schools offering Seneca II training but as far as JAA training goes IFTA is the only one with Seneca II.
Just out of interest, why do you want to train in Seneca 2?