It is an interesting fact that lots of Germans do not use electronic payment methods that function beyond Germany's borders, such as PayPal or even credit cards. If you want to do a bank-to-bank transfer then get from the seller his IBAN reference including the SWIFT code for his/her branch (UK banks have now for some years adopted the international account referencing system, rather late but they now have). Armed with these go to your bank and make the arrangements over the counter - make certain you undertake to pay all transfer fees because otherwise the seller may get less than you promised to pay if the receiving bank charges a fee.
On the other hand, when buying from Germany on eBay, I have several times simply sent cash euro(wrapped in thin aluminium foil) in a normal envelope - this has always worked and I have never had problems with the transactions. This payment method is low risk if the transaction is of relatively low value, and I simply rounded up in order to send only paper money. Sometimes (i.e. if the rounding involved a significant increment) I asked for the coin change to be taped to the item when it was sent.