Can anyone explain the best course of action, I've informed seller they'd be able to recover the BTC from their BCC wallet but they answered as if I hadn't done the mistake already, I'd like simple step by step guide how they can recover it to send to them.
Step 1) Open Bitcoin ABC (or other BCH client) containing the wallet with the address: 12PYBy89CUJkoJyar48E2Shys7GBMY4CxJ .
Step 2) Export private key of the address: 12PYBy89CUJkoJyar48E2Shys7GBMY4CxJ.
Step 3) Import private key using Bitcoin Core, Electrum or other
Bitcoin wallets.
Step 4) Send BTC back to the sender.
This is really trivial. I don't see how anyone could have trouble following this.