To clarify how to apply for a refund:
Just send an email stating you want one.
But i need to extra Informations:

Order number(s) > very important, saves me from having to look it up.

In case of paypal thats all.

If you paid via bank wire, i will need the IBAN and BIC to send the refund to.

Now to the most difficult case: Bitcoin
I have bitpay configured to Pay me directly in Euros so i never really received any Bitcoins directly.
To issue a refund through them i need to give them Bitcoins.  
That means i have to buy BTC first to be able to refund the bitpay payments.
For all EU customers a SEPA refund will be faster and easier for me.
If you want BTC, i will refund BTC.
Please note that the current bitpay eur<->btc exchange rate at the time the refund takes place will be applied.
And don't forget to provide me with the BTC address to refund to.