Don't think you need base training for an ac you hold a non-JAA TR for. However, I've abandoned my goal of converting this way due to
1. The lack of JAA CRJ sims + willingness of the 2 TRTO's to offer any kind of meaningful dialogue about this kind of program.
2. The huge amount of money and bureaucracy involved in flying out a CAA Flt Ops inspector for an observation ride, plus the very high risk of a partial and a further outlay and delay for the re-check.
I'm going to get a quick and dirty CPL ME IR and call it good!