Big Bore,
I feel for you mate. There is nothing worse then paying out good money for a new rifle that won't shoot. I must admit that I have no experience of the 550's other than that a mate has one in 375H&H and it seems to shoot & feed well. He likes it, especially for the Money!
I own 2 CZ/BRNO's both both are model 602's. One is in 375H&H and the other in 458Win. The 375H&H is a dream. shoots just about any load very well, never has had a feed problem. And I wouldn't part with it for quids.I've owned the 375 for over 20 years. The 458 on the other hand, well she can be a bitch! She has had feed problems since the day I bought her. The only way to get her to feed is by using solid projectiles only. She is accurate though. Still I love the all steel actions and if I ever do go after something big and or bity and want a 458, I'd probably send her off to a good gun smith and spend what ever was needed to fix her feed problem.
I hope that your CZ problems are fixed quickly.
Good luck & regards
Rod