I suggest checking out rimfire central: http://www.rimfirecentral.com/forums/index.php
. More information than you could possibly need in the cz section.
The big difference, as I understand, between the 452 and 455 is the ability to change calibers by changing the barrel. The new 455's give you the option. Some say accuracy may be the trade off. I don't know as I don't own the 455.
The difference between the Trainer and the other models (American, Varmint, etc) is the type of wood and the sights. The trainer has birch and tangent sights. I am not sure about the 455 lux sights. I think the 452 lux and ultralux had the same sights as the trainer. It sounds as if you have the ability to put your hands on the rifle before you purchase so check out the quality of wood and sights.
You may have a hard time finding a 452 in a model other than the trainer.
Edit: caution - the are highly addictive!