As I said, international transfer, just like you would pay any other bill using online banking but they put a £15GBP charge onto it as it is international and you probably don't get the best exchange rate either. Cost for SEPA is £19GBP. That is the cost to me, Torsten then gets charged by his bank for accepting that payment so you have to cover that cost too.
Torsten is not set up for any online payment be that by card or Paypal and will send you an invoice on receipt of order with his bank details, upto you to find a way to get the money there. I expect it is easier for German customers and maybe other countries that use the Euro.