I would like to chcek the route before I buy maps becouse I want to buy new ones, next year.
The cost of maps will be pretty marginal compared to what the trip is going to cost you. Anyway, there are several online route planning sites. Here's one:
SkyDemon Light
That should give you an idea about distances, airspace and such.
PM me if you need help in Rotterdam. That's where I am based.
In Poland we have AIP on the internet, it is obviously not for operational use but most information is up to date. Does it work in your countries too?
If Poland puts the AIP online (assuming it's current and not something outdated), why would you NOT use that for operational use?
Anyway, most European countries put the AIP online (Germany is one exception I know of). You can either go to each countries CAA site, or whoever handles the dissemination of aeronautical information. But for these sort of things, Eurocontrol is a much easier source.
You are going to need to create an account for "EAD Basic", then look for an application called PAMS Light. It essentially contains all the CIV and MIL AIPs for Europe, insofar they're available publicly.
EUROCONTROL - The European AIS Database: Introduction to EAD Basic - Home