I haven't tried a 17 hmr barrel on my CZ 455 (American), but I can tell you it is a great gun for the money in .22lr.
17 or .22 would both work towards practice. Watch your .22 sub sonic bullets arc through the air on the way to hitting the paper through a 20 power scope (at 100 yds). Good times.
I have several rimfires. My savage .22 wmr is nice, my marlin 17 hmr is very accurate (especially for the price), my ruger can send a lot of rounds downrange quickly, but the fun factor for me is with the cz (in .22lr). I like the feel and performance of the cz, I like plinking with the .22 and I like shooting with bolt rifles.