Unfortunately blocking him is not a solution because he does not have a static ip (Germany ips always), each time he registers with a different e-mail (google, yahoo etc) and the police report is a very sad story here in Greece. Have asked my lawyer and told me that the only way is to sue him for the police to start acting and this case will finally go to court in about six years.
Also tried to contact PayPal, explained the situation, asked how i can block him permanently from sending payments to me, but they never replied. In their forums, they give a way to block a user, but if he has set his paypal account not to be viewable by others, you can not find him to block him.
This is why i thought of the auto refund solution.
Right now i do not accept registrations from Germany but you understand this is one country minus to the site's income.
Thank you