In reply to Enty:
Unaccompanied personal items and sporting goods you fill out a declaration form in duplicate, the customs stamp it and retain one copy. Depending on the value you either pay the import duty up front or a suitable security i.e. what the customs officer thinks. This is returned when you again leave.
It has always been like this previous to joining the EU, when I was regularly travelling into Europe with race motorcycles there is a customs bond system for commercial goods which can also serve the same purpose, that is you don't have to carry wads of cash or a bank draft with you. One pitfall can be the import value into say Holland is vastly higher than the value in your own country which is where the bond system through an agent will cover this.
They don't care what you are doing!