This book contains some solutions in English:

http://www.lookingforachallengethebook.com/

However, the book seems to be nearly impossible to get.

I think that the best solution is to learn some Polish, it's not so difficult to read. :)

This site has quite a lot of problems with test cases provided (under "Useful resources"), you could at least try to practice this way. But maybe you're looking for solutions of some specific problems?

Of course, there's still the method of "write an e-mail to the problemsetters themselves", which might be more effective.