Have you tried online resources like polishgrammar.com or mowicpopolsku.com ? Also from my own experience all the carboots, charity shops, etc. always have some foreign language books.

Memrise will help you - http://www.memrise.com/courses/english/polish/

Thanks Kuba

Oh, sorry, on the right side, there's an English version. You will find nothing better, I assume.

And here, only in Polish, though, but superb, in my opinion: http://grzegorj.w.interia.pl/gram/gram00.html