Just a little correction which you perhaps may find useful. Although you put the word "intermediate" before the "coursebook/textbook" noun in English, in Polish you should say: "podręcznik do nauki polskiego dla średniozaawansowanych".
Good luck for you in finding an appropriate book!
You're right about the Po Polsku books being more for classroom learning, but they are still very doable on your own - even better if you get a Polish friend to do the speaking exercises with you. The listening exercises are fine for doing alone.
When it comes to learning grammar, I can recommend Bana Bielec's Intermediate Polish - you'll find it on the internet, definitely amazon. Once you've finished that then you won't have too many grammar questions left to ask!
But yeah, Po Polsku 2 and 3 are pretty decent.
The hurra po polsku books are great if you have a tutor, or are learning in a class, but I wouldn't recommend using them on your own. The books are completely in Polish, and without a tutor, they won't explain to you clearly why things are. They are perfect to go through as additional practice though, once you have learnt the material elsewhere. If on the other hand you have someone who can go through the book with you, then I highly recommend them.
However, for working on your own I would recommend, "cześć jak się masz II". This is at level A2 in Polish and it is a very good course book. There are dialogs, good explanations, and lots of chances to practice. There is even an assessment test at the end of the book. Also, unlike some other Polish books, I found this one pleasant to look at, and nicely illustrated. The book flows on nicely from the previous level A1 book, and there are also additional more advanced books that follow for level B1, B2, etc..
